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{{short description|Capacity for consciously making sense of things}}
{{about|the human faculty of reason and rationality}}
{{Epistemology sidebar}}
'''Reason''' is the capacity of [[Consciousness|consciously]] applying [[logic]] by [[Logical consequence|drawing valid conclusions]] from new or existing [[information]], with the aim of seeking [[truth]].<ref>{{multiref2
|1={{Cite book|last=Proudfoot|first=Michael|title=The Routledge dictionary of philosophy|date=2010|publisher=Routledge|others=A. R. Lacey|isbn=978-0203428467|edition=4th|location=London|pages=341|oclc=503050369|quote=Reason: A general faculty common to all or nearly all humans... this faculty has seemed to be of two sorts, a faculty of intuition by which one 'sees' truths or abstract things ('essences' or universals, etc.), and a faculty of reasoning, i.e. passing from premises to a conclusion (discursive reason). The verb 'reason' is confined to this latter sense, which is now anyway the commonest for the noun too}}
|2={{Cite book|last=Rescher|first=Nicholas|title=The Oxford companion to philosophy|publisher=Oxford University Press|others=Ted Honderich|year=2005|isbn=978-0191532658|edition=2nd|location=Oxford|pages=791|oclc=62563098|quote=reason. The general human 'faculty' or capacity for truth-seeking and problem solving}}
}}</ref> It is associated with such characteristically [[human]] activities as [[philosophy]], [[religion]], [[science]], [[language]], and [[mathematics]], and is normally considered to be a distinguishing ability possessed by humans.<ref>{{multiref2
|1={{cite book |last1=Mercier |first1=Hugo |last2=Sperber |first2=Dan |author-link2=Dan Sperber |date=2017 |title=The Enigma of Reason |location=Cambridge, MA |publisher=[[Harvard University Press]] |isbn=978-0674368309 |oclc=959650235 |page=[https://books.google.com/books?id=zc-WDgAAQBAJ&pg=PA2 2] |quote=Enhanced with reason, cognition can secure better knowledge in all domains and adjust action to novel and ambitious goals, or so the story goes.... Understanding why only a few species have echolocation is easy. Understanding why only humans have reason is much more challenging.}}
|2=Compare: {{cite book |last1=MacIntyre |first1=Alasdair |author-link1=Alasdair MacIntyre |title=Dependent Rational Animals: Why Human Beings Need the Virtues |url=https://books.google.com/books?id=Jv9Jx5iQ4uYC |series=The Paul Carus Lectures |volume=20 |publisher=[[Open Court Publishing]] |date=1999 |isbn=978-0812693973 |oclc=40632451 |access-date=2014-12-01 |quote=[T]he exercise of independent practical reasoning is one essential constituent to full human flourishing. It is not—as I have already insisted—that one cannot flourish at all, if unable to reason. Nonetheless not to be able to reason soundly at the level of practice is a grave disability.}}
}}</ref><ref>{{cite web |last1=Swindal |first1=James |title=Faith: Historical Perspectives |url=https://iep.utm.edu/faith-re/ |website=Internet Encyclopedia of Philosophy |publisher=Duquesne University |access-date=December 18, 2023}}</ref> Reason is sometimes referred to as [[rationality]],<ref>{{multiref2
|1={{cite book |editor1-last=Amoretti |editor1-first=Maria Cristina |editor2-last=Vassallo |editor2-first=Nicla |editor2-link=Nicla Vassallo |date=2013 |title=Reason and Rationality |series=Philosophische Analyse / Philosophical Analysis |volume=48 |location=Berlin |publisher=[[De Gruyter]] |isbn=978-3868381634 |oclc=807032616 |doi=10.1515/9783110325867 }}
|2={{cite book |last=Audi |first=Robert |author-link=Robert Audi |date=2001 |title=The Architecture of Reason: The Structure and Substance of Rationality |location=Oxford; New York |publisher=Oxford University Press |isbn=0195141121 |oclc=44046914 |doi=10.1093/acprof:oso/9780195158427.001.0001 }}
|3={{cite book |last=Eze |first=Emmanuel Chukwudi |author-link=Emmanuel Chukwudi Eze |date=2008 |title=On Reason: Rationality in a World of Cultural Conflict and Racism |location=Durham, NC |publisher=[[Duke University Press]] |isbn=978-0822341789 |oclc=180989486 |doi=10.1215/9780822388777 }}
|4={{cite book |last=Rescher |first=Nicholas |author-link=Nicholas Rescher |date=1988 |title=Rationality: A Philosophical Inquiry into the Nature and the Rationale of Reason |series=Clarendon Library of Logic and Philosophy |location=Oxford; New York |publisher=[[Clarendon Press]]; [[Oxford University Press]] |isbn=0198244355 |oclc=17954516}}
}}</ref> although the latter is more about its application.

'''Reasoning''' involves using more-or-less rational processes of [[Thought|thinking]] and [[cognition]] to extrapolate from one's existing knowledge to generate new knowledge, and involves the use of one's [[intellect]]. The field of <span lang="en" dir="ltr">logic</span> studies the ways in which humans can use '''formal reasoning'''<!--boldface per [[WP:R#PLA]]--> to produce [[Validity (logic)|logically valid]] [[argument]]s and true conclusions.<ref>{{cite encyclopedia|last= Hintikka|first=J.|title=Philosophy of logic|url=http://www.britannica.com/EBchecked/topic/346240/philosophy-of-logic|encyclopedia=Encyclopædia Britannica|publisher= Encyclopædia Britannica, Inc.|access-date=12 November 2013|author-link=Jaako Hintikka}}</ref> Reasoning may be subdivided into [[Logical form|forms]] of [[logical reasoning]], such as [[deductive reasoning]], [[inductive reasoning]], and [[abductive reasoning]].

[[Aristotle]] drew a distinction between logical '''discursive reasoning'''<!--boldface per [[WP:R#PLA]]--> (reason proper), and [[Intuition (psychology)|intuitive reasoning]],<ref name=NE>{{cite book|author=[[Aristotle]]|title=[[Nicomachean Ethics]]}}</ref>{{rp|at=[https://standardebooks.org/ebooks/aristotle/nicomachean-ethics/f-h-peters/text/book-6#chapter-6-1-7 VI.7]}} in which the reasoning process through intuition—however valid—may tend toward the personal and the subjectively opaque. In some social and political settings logical and intuitive modes of reasoning may clash, while in other contexts intuition and formal reason are seen as complementary rather than adversarial. For example, in [[mathematics]], intuition is often necessary for the creative processes involved with arriving at a [[formal proof]], arguably the most difficult of formal reasoning tasks.

Reasoning, like [[habit]] or [[intuition]], is one of the ways by which thinking moves from one idea to a related idea. For example, reasoning is the means by which rational individuals understand the significance of sensory information from their environments, or conceptualize abstract dichotomies such as [[Causality|cause and effect]], [[truth]] and [[False (logic)|falsehood]], or [[good and evil]]. Reasoning, as a part of [[Executive functions|executive decision making]], is also closely identified with the ability to self-consciously change, in terms of [[goal]]s, [[belief]]s, [[attitude (psychology)|attitudes]], [[tradition]]s, and [[institution]]s, and therefore with the capacity for [[freedom]] and [[self-determination]].<ref>{{multiref2|1={{cite book|first=Michel|last=Foucault|chapter=What is Enlightenment?|title=The Essential Foucault|editor-first1=Paul|editor-last1=Rabinow|editor-first2=Nikolas|editor-last2=Rose|location=New York|publisher=The New Press|year=2003|pages=43–57}}
|2={{cite journal | last=Kompridis | first=Nikolas | title=So We Need Something Else for Reason to Mean | journal=International Journal of Philosophical Studies | publisher=Informa UK Limited | volume=8 | issue=3 | year=2000 | issn=0967-2559 | doi=10.1080/096725500750039282 | pages=271–295| s2cid=171038942 }}
|3={{cite book|first=Nikolas|last=Kompridis|chapter=The Idea of a New Beginning: A Romantic Source of Normativity and Freedom|title=Philosophical Romanticism|location=New York|publisher=Routledge|year=2006|pages=32–59}}
}}</ref>

[[Psychologist]]s and [[Cognitive science|cognitive scientists]] have attempted to study and explain [[psychology of reasoning|how people reason]], e.g. which cognitive and neural processes are engaged, and how cultural factors affect the inferences that people draw. The field of [[automated reasoning]] studies how reasoning may or may not be modeled computationally. [[comparative psychology|Animal psychology]] considers the question of whether animals other than humans can reason.

==Etymology and related words==
In the [[English language]] and other modern [[Languages of Europe|European languages]], "reason", and related words, represent words which have always been used to translate Latin and classical Greek terms in their philosophical sense.
* The original [[Greek language|Greek]] term was {{lang|grc|"λόγος"}} {{transliteration|grc|[[wikt:logos#Greek|logos]]}}, the root of the modern English word "[[logic]]" but also a word that could mean for example "speech" or "explanation" or an "account" (of money handled).<ref>{{multiref2
|1={{cite book|first1=Henry George |last1=Liddell| first2=Robert |last2=Scott|title=A Greek–English Lexicon|chapter-url=https://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A1999.04.0057%3Aentry%3Dlo%2Fgos|chapter=logos|year=1940|location=Oxford|publisher=Clarendon Press}}
|2={{cite web|url=https://www.merriam-webster.com/dictionary/logic?show=0&t=1296722456#word-history|title=Word History: logic|website=Merriam Webster Dictionary|date=14 September 2023 }}
}}</ref>
* As a philosophical term {{transliteration|grc|logos}} was translated in its non-linguistic senses in [[Latin]] as {{lang|la|[[wikt:ratio#Latin|ratio]]}}. This was originally not just a translation used for philosophy, but was also commonly a translation for {{transliteration|grc|logos}} in the sense of an account of money.<ref>{{Citation|chapter-url=https://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A1999.04.0059%3Aentry%3Dratio|chapter=ratio|first1=Charlton |last1=Lewis|first2= Charles |last2=Short|title=A Latin Dictionary}}</ref>
* [[French language|French]] {{lang|fr|[[wikt:raison|raison]]}} is derived directly from Latin, and this is the direct source of the English word "reason".<ref name=mw/>

The earliest major philosophers to publish in English, such as [[Francis Bacon]], [[Thomas Hobbes]], and [[John Locke]] also routinely wrote in Latin and French, and compared their terms to Greek, treating the words "{{transliteration|grc|logos}}", "{{lang|la|ratio}}", "{{lang|fr|raison}}" and "reason" as interchangeable. The meaning of the word "reason" in senses such as "human reason" also overlaps to a large extent with "[[rationality]]" and the adjective of "reason" in philosophical contexts is normally "[[Rationality|rational]]", rather than "reasoned" or "reasonable".<ref>{{multiref2
|1={{cite web|url=https://www.merriam-webster.com/dictionary/rational|title=rational|website=Merriam Webster Dictionary|date=13 September 2023 }}
|2={{cite web|url=https://www.merriam-webster.com/dictionary/reasonable|title=reasonable|website=Merriam Webster Dictionary|date=12 September 2023 }}
}}</ref> Some philosophers, Hobbes for example, also used the word '''ratiocination'''<!--boldface per [[WP:R#PLA]]--> as a synonym for "reasoning".

In contrast to the use of "reason" as an [[Noun#Concrete nouns and abstract nouns|abstract noun]], [[Reason (argument)|''a'' reason]] is a consideration that either explains or justifies events, phenomena, or [[behavior]].<ref name=mw>{{cite web|url=https://www.merriam-webster.com/dictionary/reason|title=reason|website=Merriam-Webster Dictionary|date=10 September 2023 }}</ref> Reasons justify decisions, reasons support explanations of natural phenomena, and reasons can be given to explain the actions (conduct) of individuals.

The words are connected in this way: using reason, or reasoning, means providing good reasons. For example, when evaluating a moral decision, "morality is, at the very least, the effort to guide one's conduct by ''reason''—that is, doing what there are the best reasons for doing—while giving equal [and impartial] weight to the interests of all those affected by what one does."<ref>{{cite book|last=Rachels|first=James|title=The Elements of Moral Philosophy|edition=4th|publisher=McGraw Hill|year=2002}}{{page needed|date=September 2023}}</ref>

==Philosophical history{{anchor|History_of_reasoning}}==
[[File:Goya Caprichos3.jpg|thumb|[[Francisco de Goya]], ''[[The Sleep of Reason Produces Monsters]]'' ({{lang|es|El sueño de la razón produce monstruos}}), {{circa|1797}}]]
The proposal that reason gives humanity a special position in nature has been argued{{cn|reason=|date=September 2023}} to be a defining characteristic of [[Western culture|western]] [[philosophy]] and later western [[History of science#Modern science|science]], starting with classical Greece. Philosophy can be described as a way of life based upon reason, while reason has been among the major subjects of philosophical discussion since ancient times. Reason is often said to be [[Reflexivity (social theory)|reflexive]], or "self-correcting", and the critique of reason has been a persistent theme in philosophy.<ref name="Jürgen Habermas 1990">{{cite book |last1=Habermas |first1=Jürgen |author-link=Jürgen Habermas |title=The Philosophical Discourse of Modernity |location=Cambridge, Mass. |publisher=MIT Press |year=1990 }}</ref>

===Classical philosophy===
For many classical [[philosophers]], nature was understood [[teleology|teleologically]], meaning that every type of thing had a definitive purpose that fit within a natural order that was itself understood to have aims. Perhaps starting with [[Pythagoras]] or [[Heraclitus]], the [[cosmos]] was even said to have reason.<ref>{{cite book|title=The Presocratic Philosophers|edition=second|last1=Kirk|last2=Raven|last3=Schofield|publisher=Cambridge University Press|year=1983|pages=204 & 235}}</ref> Reason, by this account, is not just a characteristic that people happen to have. Reason was considered of higher stature than other characteristics of human nature, because it is something people share with nature itself, linking an apparently immortal part of the human mind with the divine order of the cosmos. Within the human [[mind]] or [[Soul (spirit)|soul]] ({{transliteration|grc|[[psyche (psychology)|psyche]]}}), reason was described by [[Plato]] as being the natural monarch which should rule over the other parts, such as spiritedness ({{transliteration|grc|[[thumos]]}}) and the passions. [[Aristotle]], Plato's student, defined human beings as [[rational animal]]s, emphasizing reason as a characteristic of [[human nature]]. He described the highest human happiness or well being ({{transliteration|grc|[[eudaimonia]]}}) as a life which is lived consistently, excellently, and completely in accordance with reason.{{r|NE|at=[[Nicomachean Ethics#Defining eudaimonia and the aim of the Ethics|I]]}}

The conclusions to be drawn from the discussions of Aristotle and Plato on this matter are amongst the most debated in the history of philosophy.<ref name=Davidson>{{cite book|title=Alfarabi, Avicenna, and Averroes, on Intellect|last=Davidson|first=Herbert|publisher=Oxford University Press|year=1992|page=3}}</ref> But teleological accounts such as Aristotle's were highly influential for those who attempt to explain reason in a way that is consistent with [[monotheism]] and the immortality and divinity of the human soul. For example, in the [[Neoplatonism|neoplatonist]] account of [[Plotinus]], the [[cosmos]] has one soul, which is the seat of all reason, and the souls of all people are part of this soul. Reason is for Plotinus both the provider of form to material things, and the light which brings people's souls back into line with their source.<ref>{{Citation|chapter=Plotinus|title=Internet Encyclopedia of Philosophy|chapter-url=https://iep.utm.edu/plotinus/|last=Moore|first=Edward}}</ref>

===Christian and Islamic philosophy===
The classical view of reason was adopted by the early Church.<ref>{{Citation|chapter=Plato and Platonism|title=Catholic Encyclopedia|chapter-url=https://www.newadvent.org/cathen/12159a.htm|last=Turner|first=William|year=1911|location=New York|publisher=Robert Appleton Company|volume=12}}</ref> The greatest among the early [[Church Fathers]] and [[Doctors of the Church]] such as [[Augustine of Hippo]], [[Basil of Caesarea]], and [[Gregory of Nyssa]] were as much Neoplatonic philosophers as they were Christian theologians, and they adopted the Neoplatonic view of human reason and its implications for our relationship to creation, to ourselves, and to God.

The Neoplatonic conception of the rational aspect of the human soul was widely adopted by medieval Islamic philosophers and continues to hold significance in [[Iranian philosophy]].<ref name=Davidson/> As European intellectual life reemerged from the [[Dark Ages (historiography)|Dark Ages]], the Christian [[Patristic]] tradition and the influence of esteemed Islamic scholars like [[Averroes]] and [[Avicenna]] contributed to the development of the [[Scholasticism|Scholastic]] view of reason, which laid the foundation for our modern understanding of this concept.<ref>{{Citation|chapter=Reason|title=Catholic Encyclopedia|chapter-url=https://www.newadvent.org/cathen/12673b.htm|last=Rahilly|first=Alfred|year=1911|location=New York|publisher=Robert Appleton Company|volume=12}}</ref>

Among the Scholastics who relied on the classical concept of reason for the development of their doctrines, none were more influential than [[Saint Thomas Aquinas]], who put this concept at the heart of his [[Natural Law]]. In this doctrine, Thomas concludes that because humans have reason and because reason is a spark of the divine, every single human life is invaluable, all humans are equal, and every human is born with an intrinsic and permanent set of basic rights.<ref>{{Citation|chapter=Natural Law|title=Catholic Encyclopedia|chapter-url=https://www.newadvent.org/cathen/09076a.htm|last=Fox|first=James|year=1910|location=New York|publisher=Robert Appleton Company|volume=9}}</ref> On this foundation, the idea of human rights would later be constructed by Spanish theologians at the [[School of Salamanca]].

Other Scholastics, such as [[Roger Bacon]] and [[Albertus Magnus]], following the example of Islamic scholars such as [[Alhazen]], emphasised reason an intrinsic human ability to decode the created order and the structures that underlie our experienced physical reality. This interpretation of reason was instrumental to the development of the scientific method in the early Universities of the high Middle Ages.<ref>{{Citation|chapter=Religion and Science|title=Stanford Encyclopaedia of Philosophy|year=2022|publisher=Metaphysics Research Lab, Stanford University|chapter-url=https://plato.stanford.edu/entries/religion-science/|first=Helen|last=De Cruz}}</ref>

===Subject-centred reason in early modern philosophy===

The [[early modern era]] was marked by a number of significant changes in the understanding of reason, starting in [[Europe]]. One of the most important of these changes involved a change in the [[metaphysics|metaphysical]] understanding of human beings. Scientists and philosophers began to question the [[teleological]] understanding of the world.<ref>{{cite web |first=Hubert |last=Dreyfus |title=Telepistemology: Descartes' Last Stand |url=http://socrates.berkeley.edu/~hdreyfus/rtf/Limits_of_Telepresence_6_99.rtf|url-status=dead|archive-url=https://web.archive.org/web/20110521043801/http://socrates.berkeley.edu/~hdreyfus/rtf/Limits_of_Telepresence_6_99.rtf|archive-date=2011-05-21 |publisher= socrates.berkeley.edu |access-date= February 23, 2011}}</ref> Nature was no longer assumed to be human-like, with its own aims or reason, and human nature was no longer assumed to work according to anything other than the same "[[Scientific law|laws of nature]]" which affect inanimate things. This new understanding eventually displaced the previous [[world view]] that derived from a spiritual understanding of the universe.
[[File:Frans Hals - Portret van René Descartes.jpg|thumb|René Descartes]]
Accordingly, in the 17th century, [[René Descartes]] explicitly rejected the traditional notion of humans as "rational animals", suggesting instead that they are nothing more than "thinking things" along the lines of other "things" in nature. Any grounds of knowledge outside that understanding was, therefore, subject to doubt.

In his search for a foundation of all possible knowledge, Descartes brought into doubt ''all'' knowledge—''except'' that of the mind itself in the process of thinking:

<blockquote>At this time I admit nothing that is not necessarily true. I am therefore precisely nothing but a thinking thing; that is a mind, or intellect, or understanding, or reason—words of whose meanings I was previously ignorant.<ref>{{cite book|last=Descartes|first=René|title=[[Meditations on First Philosophy]]|chapter=Concerning the Nature of the Human Mind|year=1641}}</ref></blockquote>

This eventually became known as [[epistemological]] or "subject-centred" reason, because it is based on the ''knowing subject'', who perceives the rest of the world and itself as a set of objects to be studied, and successfully mastered, by applying the knowledge accumulated through such study. Breaking with tradition and with many thinkers after him, Descartes explicitly did not divide the incorporeal soul into parts, such as reason and intellect, describing them instead as one indivisible incorporeal entity.

A contemporary of Descartes, [[Thomas Hobbes]] described reason as a broader version of "addition and subtraction" which is not limited to numbers.<ref>{{Citation|chapter=Of Philosophy|title=Elements of Philosophy I: De Corpore|url=https://archive.org/details/englishworkstho21hobbgoog|last=Hobbes|first=Thomas|editor-first=William|editor-last=Molesworth|location=London|publisher=J. Bohn|year=1839|orig-year=1655|page=5|quote=We must not therefore think that computation, that is, ratiocination, has place only in numbers, as if man were distinguished from other living creatures (which is said to have been the opinion of ''[[Pythagoras]]'') by nothing but the faculty of numbering; for ''magnitude, body, motion, time, degrees of quality, action, conception, proportion, speech and names'' (in which all the kinds of philosophy consist) are capable of addition and substraction {{sic}}. Now such things as we add or substract, that is, which we put into an account, we are said to ''consider'', in Greek {{lang|grc|λογίζεσθαι}} [{{transliteration|grc|logizesthai}}], in which language also {{lang|grc|συλλογίζεσθι}} [{{transliteration|grc|syllogizesthai}}] signifies to ''compute'', ''reason'', or ''reckon''.}}</ref> This understanding of reason is sometimes termed "calculative" reason. Similar to Descartes, Hobbes asserted that "No discourse whatsoever, can end in absolute knowledge of fact, past, or to come" but that "sense and memory" is absolute knowledge.<ref>{{multiref2
|1={{citation|first=Thomas|last=Hobbes|title=Leviathan|chapter=Of the ends, or resolutions of discourse|chapter-url=https://archive.org/details/in.ernet.dli.2015.224021/page/n65/mode/2up|year=1651}}
|2={{citation|first=Thomas|last=Hobbes|title=Leviathan|chapter=Of the several subjects of knowledge|chapter-url=https://archive.org/details/in.ernet.dli.2015.224021/page/n76/mode/1up|year=1651}}
}}</ref>

In the late 17th century through the 18th century, [[John Locke]] and [[David Hume]] developed Descartes's line of thought still further. Hume took it in an especially [[skepticism|skeptical]] direction, proposing that there could be no possibility of [[deductive reasoning|deducing]] relationships of cause and effect, and therefore no knowledge is based on reasoning alone, even if it seems otherwise.<ref>{{multiref2
|1={{cite book|first=John|last=Locke|chapter=Of Identity and Diversity|year=1689|chapter-url=https://archive.org/details/in.ernet.dli.2015.223061/page/n257/mode/2up|title=An Essay concerning Human Understanding|volume=II}}
|2={{cite book|first=David |last=Hume|chapter=Of Personal Identity|chapter-url=https://archive.org/details/0213-bk/page/251/mode/1up|title=A Treatise of Human Nature|volume=I.4|year=1740}}
}}</ref>

Hume famously remarked that, "We speak not strictly and philosophically when we talk of the combat of passion and of reason. Reason is, and ought only to be the slave of the passions, and can never pretend to any other office than to serve and obey them."<ref>{{citation|first=David |last=Hume|chapter=Of the influencing motives of the will|chapter-url=https://archive.org/details/0213-bk/page/413/mode/1up|title=A Treatise of Human Nature|volume=II.3|year=1740}}</ref> Hume also took his definition of reason to unorthodox extremes by arguing, unlike his predecessors, that human reason is not qualitatively different from either simply conceiving individual ideas, or from judgments associating two ideas,<ref>{{citation|first=David |last=Hume|chapter=Of the Nature of the Idea Or Belief|chapter-url=https://archive.org/details/0213-bk/page/94/mode/1up8|title=A Treatise of Human Nature|volume=I.3|year=1740|at=[https://archive.org/details/0213-bk/page/96/mode/1up footnote 1]}}</ref> and that "reason is nothing but a wonderful and unintelligible instinct in our souls, which carries us along a certain train of ideas, and endows them with particular qualities, according to their particular situations and relations."<ref name=HumeI3xvi>{{citation|first=David |last=Hume|chapter=Of the reason of animals|chapter-url=https://archive.org/details/0213-bk/page/176/mode/2up|title=A Treatise of Human Nature|volume=I.3|year=1740}}</ref> It followed from this that animals have reason, only much less complex than human reason.

In the 18th century, [[Immanuel Kant]] attempted to show that Hume was wrong by demonstrating that a "[[transcendental arguments|transcendental]]" self, or "I", was a necessary condition of all experience. Therefore, suggested Kant, on the basis of such a self, it is in fact possible to reason both about the conditions and limits of human knowledge. And so long as these limits are respected, reason can be the vehicle of morality, justice, aesthetics, theories of knowledge ([[epistemology]]), and understanding.{{cn|reason=|date=September 2023}}<ref>{{Cite web |title=The critique of pure reason |url=https://www.marxists.org}}</ref>

===Substantive and formal reason===

In the formulation of Kant, who wrote some of the most influential modern treatises on the subject, the great achievement of reason ({{langx|de|Vernunft}}) is that it is able to exercise a kind of universal law-making. Kant was able therefore to reformulate the basis of moral-practical, theoretical, and aesthetic reasoning on "universal" laws.

Here, [[practical reason]]ing is the self-legislating or self-governing formulation of universal [[norm (philosophy)|norms]], and [[theory|theoretical]] reasoning is the way humans posit universal [[natural law|laws of nature]].<ref>{{multiref2
|1={{cite book|first=Immanuel|last=Kant|author-link=Immanuel Kant|title=[[Critique of Pure Reason]]|year=1781}}
|2={{cite book|first=Immanuel|last=Kant|author-link=Immanuel Kant|title=[[Critique of Practical Reason]]|year=1788}}
}}</ref>

Under practical reason, the moral [[autonomy]] or freedom of people depends on their ability, by the proper exercise of that reason, to behave according to laws that are given to them. This contrasted with earlier forms of morality, which depended on [[religion|religious understanding]] and interpretation, or on [[nature]], for their substance.<ref>{{cite book|first=Michael|last=Sandel|title=Justice: What's the Right Thing to Do?|location=New York|publisher=Farrar, Straus and Giroux|year=2009}}</ref>

According to Kant, in a free society each individual must be able to pursue their goals however they see fit, as long as their actions conform to principles given by reason. He formulated such a principle, called the "[[categorical imperative]]", which would justify an action only if it could be universalized:
<blockquote>Act only according to that maxim whereby you can, at the same time, will that it should become a universal law.<ref name="Ellington">{{cite book|last1=Kant|first1=Immanuel|author-link=Immanuel Kant|translator-first=James W.|translator-last=Ellington|orig-year=1785|title=Grounding for the Metaphysics of Morals|edition=3rd|publisher=Hackett|year=1993|page=[https://archive.org/details/groundingformet000kant/page/30 30]|isbn=978-0872201668|url=https://archive.org/details/groundingformet000kant}}</ref></blockquote>

In contrast to Hume, Kant insisted that reason itself (German {{lang|de|[[wikt:Vernunft|Vernunft]]}}) could be used to find solutions to metaphysical problems, especially the discovery of the foundations of morality. Kant claimed that these solutions could be found with his "[[transcendental logic]]", which unlike normal logic is not just an instrument that can be used indifferently, as it was for Aristotle, but a theoretical science in its own right and the basis of all the others.<ref>{{multiref2
|1={{cite book|last=Velkley|first=Richard|year=2002|chapter=On Kant's Socratism|title=Being After Rousseau|publisher=University of Chicago Press}}
|2={{cite book|first=Immanuel|last=Kant|author-link=Immanuel Kant|title=[[Critique of Pure Reason]]|year=1781|at=Preface}}
}}</ref>

According to [[Jürgen Habermas]], the "substantive unity" of reason has dissolved in modern times, such that it can no longer answer the question "How should I live?" Instead, the unity of reason has to be strictly formal, or "procedural". He thus described reason as a group of three autonomous spheres (on the model of Kant's three critiques):

; Cognitive–instrumental reason: the kind of reason employed by the sciences; used to observe events, to predict and control outcomes, and to intervene in the world on the basis of its hypotheses
; Moral–practical reason: what we use to deliberate and discuss issues in the moral and political realm, according to universalizable procedures (similar to Kant's categorical imperative)
; Aesthetic reason: typically found in works of art and literature, and encompasses the novel ways of seeing the world and interpreting things that those practices embody

For Habermas, these three spheres are the domain of experts, and therefore need to be mediated with the "[[lifeworld]]" by philosophers. In drawing such a picture of reason, Habermas hoped to demonstrate that the substantive unity of reason, which in pre-modern societies had been able to answer questions about the good life, could be made up for by the unity of reason's formalizable procedures.<ref>{{cite book|first=Jürgen|last=Habermas|author-link=Jürgen Habermas|title=Moral Consciousness and Communicative Action|location=Cambridge, Mass.|publisher=MIT Press|year=1995}}</ref>

===The critique of reason===

[[Johann Georg Hamann|Hamann]], [[Johann Gottfried Herder|Herder]], [[Immanuel Kant|Kant]], [[Georg Wilhelm Friedrich Hegel|Hegel]], [[Søren Kierkegaard|Kierkegaard]], [[Friedrich Nietzsche|Nietzsche]], [[Martin Heidegger|Heidegger]], [[Michel Foucault|Foucault]], [[Richard Rorty|Rorty]], and many other philosophers have contributed to a debate about what reason means, or ought to mean. Some, like Kierkegaard, Nietzsche, and Rorty, are skeptical about subject-centred, universal, or instrumental reason, and even skeptical toward reason as a whole. Others, including Hegel, believe that it has obscured the importance of [[intersubjectivity]], or "spirit" in human life, and they attempt to reconstruct a model of what reason should be.

Some thinkers, e.g. Foucault, believe there are other ''forms'' of reason, neglected but essential to modern life, and to our understanding of what it means to live a life according to reason.<ref name="Jürgen Habermas 1990"/> Others suggest that there is not just one reason or rationality, but multiple possible systems of reason or rationality which may conflict (in which case there is no super-rational system one can appeal to in order to resolve the conflict).<ref>{{multiref2|1={{cite book|first=Robert|last=Nozick|author-link=Robert Nozick|title=The Nature of Rationality|url=https://archive.org/details/natureofrational0000nozi_l8f5|url-access=registration|year=1993}}{{page needed|date=September 2023}}
|2={{cite book|first=Alasdair|last=MacIntyre|author-link=Alasdair MacIntyre|title=Whose Justice? Which Rationality?|url=https://archive.org/details/whosejusticewhic0000maci|url-access=registration|year=1988}}
}}</ref>

In the last several decades, a number of proposals have been made to "re-orient" this critique of reason, or to recognize the "other voices" or "new departments" of reason:

For example, in opposition to subject-centred reason, Habermas has proposed a model of [[communicative rationality|communicative reason]] that sees it as an essentially cooperative activity, based on the fact of linguistic [[intersubjectivity]].<ref>{{cite book|first=Jürgen|last=Habermas|title=The Theory of Communicative Action: Reason and the Rationalization of Society|translator-first=Thomas|translator-last=McCarthy|location=Boston|publisher=Beacon Press|year=1984}}</ref>

[[Nikolas Kompridis]] proposed a widely encompassing view of reason as "that ensemble of practices that contributes to the opening and preserving of openness" in human affairs, and a focus on reason's possibilities for social change.<ref>{{multiref2
|1={{cite book|first=Nikolas|last=Kompridis|title=Critique and Disclosure: Critical Theory between Past and Future|location=Cambridge, Mass.|publisher=MIT Press|year=2006}}
|2={{cite journal|first=Nikolas|last=Kompridis|doi=10.1080/096725500750039282|title=So We Need Something Else for Reason to Mean|journal=International Journal of Philosophical Studies|date=2000 |volume=8|number=3|pages=271–295|s2cid=171038942 }}
}}</ref>

The philosopher [[Charles Taylor (philosopher)|Charles Taylor]], influenced by the 20th century German philosopher [[Martin Heidegger]], proposed that reason ought to include the faculty of [[world disclosure|disclosure]], which is tied to the way we make sense of things in everyday life, as a new "department" of reason.<ref>{{cite book|first=Charles|last=Taylor|title=Philosophical Arguments|publisher=Harvard University Press|year=1997|pages=12, 15|isbn=978-0674664777}}</ref>

In the essay "What is Enlightenment?", Michel Foucault proposed a critique based on Kant's distinction between "private" and "public" uses of reason:<ref>{{cite book|first=Michel|last=Foucault|author-link=Michel Foucault|chapter=What is Enlightenment?|title=The Essential Foucault|location=New York|publisher=The New Press|year=2003|pages=43–57}}</ref>
; Private reason : the reason that is used when an individual is "a cog in a machine" or when one "has a role to play in society and jobs to do: to be a soldier, to have taxes to pay, to be in charge of a parish, to be a civil servant"
; Public reason : the reason used "when one is reasoning as a reasonable being (and not as a cog in a machine), when one is reasoning as a member of reasonable humanity"; in these circumstances, "the use of reason must be free and public"

==Reason compared to related concepts==

===Reason compared to logic===
{{See also|Logic}}
The terms ''logic'' or ''logical'' are sometimes used as if they were identical with ''reason'' or ''rational'', or sometimes logic is seen as the most pure or the defining form of reason: "Logic is about reasoning—about going from premises to a conclusion.&nbsp;... When you do logic, you try to clarify reasoning and separate good from bad reasoning."<ref>{{cite book |last=Gensler |first=Harry J. |date=2010 |title=Introduction to Logic |edition=2nd |location=New York |publisher=[[Routledge]] |page=1 |isbn=978-0415996501 |oclc=432990013 |doi=10.4324/9780203855003}}</ref> In modern [[economics]], [[Rational choice theory|rational choice]] is assumed to equate to logically [[Consistency|consistent]] choice.<ref>{{cite book |last=Gächter |first=Simon |date=2013 |chapter=Rationality, social preferences, and strategic decision-making from a behavioral economics perspective |editor1-last=Wittek |editor1-first=Rafael |editor2-last=Snijders |editor2-first=T. A. B. |editor3-last=Nee |editor3-first=Victor |title=The Handbook of Rational Choice Social Research |location=Stanford, CA |publisher=Stanford Social Sciences, an imprint of [[Stanford University Press]] |pages=33–71 (33) |isbn=978-0804784184 |oclc=807769289 |doi=10.1515/9780804785501-004 |s2cid=242795845 |quote=The central assumption of the rational choice approach is that decision-makers have logically consistent goals (whatever they are), and, given these goals, choose the best available option.}}</ref>

However, reason and logic can be thought of as distinct—although logic is one important aspect of reason. Author [[Douglas Hofstadter]], in ''[[Gödel, Escher, Bach]]'', characterizes the distinction in this way: Logic is done inside a system while reason is done outside the system by such methods as skipping steps, working backward, drawing diagrams, looking at examples, or seeing what happens if you change the rules of the system.<ref>{{cite book |last=Hofstadter |first=Douglas R. |author-link=Douglas Hofstadter |date=1999 |orig-year=1979 |title=Gödel, Escher, Bach: An Eternal Golden Braid |edition=20th anniversary |location=New York |publisher=[[Basic Books]] |isbn=0394756827 |oclc=40724766}}</ref> Psychologists Mark H. Bickard and Robert L. Campbell argue that "rationality cannot be simply assimilated to logicality"; they note that "human knowledge of logic and [[Formal system#Logical system|logical systems]] has developed" over time through reasoning, and logical systems "can't construct new logical systems more powerful than themselves", so reasoning and rationality must involve more than a system of logic.<ref>{{cite journal |last1=Bickhard |first1=Mark H. |last2=Campbell |first2=Robert L. |date=July 1996 |title=Developmental aspects of expertise: rationality and generalization |journal=[[Journal of Experimental & Theoretical Artificial Intelligence]] |volume=8 |issue=3–4 |pages=399–417 |doi=10.1080/095281396147393}}</ref><ref name=Moshman2004>{{cite journal |last=Moshman |first=David |date=May 2004 |title=From inference to reasoning: the construction of rationality |journal=Thinking & Reasoning |volume=10 |issue=2 |pages=221–239 |doi=10.1080/13546780442000024 |s2cid=43330718 |url=https://digitalcommons.unl.edu/edpsychpapers/44/|url-access=subscription }}</ref> Psychologist David Moshman, citing Bickhard and Campbell, argues for a "[[metacognitive]] conception of rationality" in which a person's development of reason "involves increasing consciousness and control of logical and other inferences".<ref name=Moshman2004/><ref>{{cite book |last=Ricco |first=Robert B. |date=2015 |chapter=The development of reasoning |editor-last=Lerner |editor-first=Richard M. |editor-link=Richard M. Lerner |title=Handbook of Child Psychology and Developmental Science |edition=7th |volume=2. Cognitive Processes |location=Hoboken, N.J. |publisher=[[John Wiley & Sons]] |pages=519–570 (534) |isbn=978-1118136850 |oclc=888024689 |doi=10.1002/9781118963418.childpsy213 |quote=Moshman's... theory of the development of deductive reasoning considers changes in metacognition to be the essential story behind the development of deductive (and inductive) reasoning. In his view, reasoning involves explicit conceptual knowledge regarding inference (metalogical knowledge) and metacognitive awareness of, and control over, inference.}}</ref>

Reason is a type of [[thought]], and [[logic]] involves the attempt to describe a system of formal rules or norms of appropriate reasoning.<ref name=Moshman2004/> The oldest surviving Western writings to explicitly consider and systematically codify the rules by which reason operates, are the works of the [[Ancient Greece|Greek]] [[philosopher]] [[Aristotle]], especially ''Prior Analytics'' and ''Posterior Analytics''.<ref>Smith, Robin. “Aristotle’s Logic and Its Influence.” In The Cambridge Companion to Aristotle, edited by Jonathan Barnes, 72–92. Cambridge University Press, 1995. https://doi.org/10.1017/CCOL0521451621.006</ref> Although the Ancient Greeks had no separate word for logic as distinct from language and reason, Aristotle's [[neologism|newly coined word]] "[[syllogism]]" ({{transliteration|grc|syllogismos}}) identified logic clearly for the first time as a distinct field of study.<ref>{{Citation |last=Smith |first=Robin |title=Aristotle's Logic |date=2017 |url=https://plato.stanford.edu/archives/fall2020/entries/aristotle-logic/ |encyclopedia=The Stanford Encyclopedia of Philosophy |editor-last=Zalta |editor-first=Edward N. |edition=Fall 2020 |publisher=Metaphysics Research Lab, Stanford University |access-date=2022-06-08}}</ref> When Aristotle referred to "the logical" ({{transliteration|grc|hē logikē}}), he was referring more broadly to rational thought.<ref>[https://www.perseus.tufts.edu/hopper/searchresults?all_words=logiko/s&all_words_expand=yes&la=greek See this Perseus search, and compare English translations.] and see [https://www.perseus.tufts.edu/hopper/morph.jsp?l=logikw%3Ds&la=greek&prior=le/getai&d=Perseus:text:1999.01.0049:book=1:section=1217b&i=1#lexicon LSJ dictionary entry for {{lang|grc|λογικός}}, section II.2.b.]</ref>

===Reason compared to cause-and-effect thinking, and symbolic thinking===
{{Main|Causality|Symbols}}
As pointed out by philosophers such as Hobbes, Locke, and Hume, some animals are also clearly capable of a type of "[[association (psychology)|associative thinking]]", even to the extent of associating causes and effects. A dog once kicked, can learn how to recognize the warning signs and avoid being kicked in the future, but this does not mean the dog has reason in any strict sense of the word. It also does not mean that humans acting on the basis of experience or habit are using their reason.{{r|HumeI3xvi}}

Human reason requires more than being able to associate two ideas—even if those two ideas might be described by a reasoning human as a cause and an effect—perceptions of smoke, for example, and memories of fire. For reason to be involved, the association of smoke and the fire would have to be thought through in a way that can be explained, for example as cause and effect. In the explanation of [[John Locke|Locke]], for example, reason requires the mental use of a third idea in order to make this comparison by use of [[syllogism]].<ref>{{cite book|first=John|last=Locke|chapter=Of Reason|year=1689|chapter-url=https://archive.org/details/in.ernet.dli.2015.223061/page/n585/mode/2up|title=An Essay concerning Human Understanding|volume=IV}}</ref>

More generally, according to [[Charles Sanders Peirce]], reason in the strict sense requires the ability to create and manipulate a system of [[symbol]]s, as well as [[Semiotic elements and classes of signs (Peirce)#II. Icon, index, symbol|indices and icons]], the symbols having only a nominal, though habitual, connection to either (for example) smoke or fire.<ref>{{cite book|first=Terrence|last=Deacon|title=The Symbolic Species: The Co-Evolution of Language and the Brain|publisher=W.W. Norton & Company|year=1998|isbn=0393317544}}</ref> One example of such a system of symbols and signs is [[language]].

The connection of reason to symbolic thinking has been expressed in different ways by philosophers. [[Thomas Hobbes]] described the creation of "Markes, or Notes of remembrance" as ''speech''.<ref>{{cite book|first=Thomas|last=Hobbes|title=Leviathan|chapter=Of speech|chapter-url=https://archive.org/details/in.ernet.dli.2015.224021/page/n47/mode/1up|year=1651}}</ref> He used the word ''speech'' as an English version of the Greek word {{transliteration|grc|[[logos]]}} so that speech did not need to be communicated.<ref>{{cite book|first=Thomas|last=Hobbes|title=Leviathan|chapter=Of speech|chapter-url=https://archive.org/details/in.ernet.dli.2015.224021/page/n47/mode/1up|year=1651|quote=The Greeks have but one word, {{transliteration|grc|logos}}, for both speech and reason; not that they thought there was no speech without reason, but no reasoning without speech}}</ref> When communicated, such speech becomes language, and the marks or notes or remembrance are called "[[Sign (linguistics)|Signes]]" by Hobbes. Going further back, although Aristotle is a source of the idea that only humans have reason ({{transliteration|grc|logos}}), he does mention that animals with imagination, for whom sense perceptions can persist, come closest to having something like reasoning and {{transliteration|grc|[[nous]]}}, and even uses the word "{{transliteration|grc|logos}}" in one place to describe the distinctions which animals can perceive in such cases.<ref>{{cite book|author=Aristotle|title=[[Posterior Analytics]]|at=II.19}}</ref>

===Reason, imagination, mimesis, and memory===
{{Main|Imagination|Mimesis|Memory|Recollection}}
Reason and [[imagination]] rely on similar [[mental processes]].<ref>{{cite book|author-link=Ruth M.J. Byrne|first=Ruth M.J.|last=Byrne|year=2005|title=The Rational Imagination: How People Create Counterfactual Alternatives to Reality|location=Cambridge, Mass.|publisher=MIT Press}}</ref> Imagination is not only found in humans. Aristotle asserted that {{transliteration|grc|phantasia}} (imagination: that which can hold images or {{transliteration|grc|phantasmata}}) and {{transliteration|grc|phronein}} (a type of thinking that can judge and understand in some sense) also exist in some animals.<ref>{{cite book|author=Aristotle|title=[[De Anima]]|at=III.1–3}}</ref> According to him, both are related to the primary perceptive ability of animals, which gathers the perceptions of different senses and defines the order of the things that are perceived without distinguishing universals, and without deliberation or {{transliteration|grc|logos}}. But this is not yet reason, because human imagination is different.

[[Terrence Deacon]] and [[Merlin Donald]], writing about the [[origin of language]], connect reason not only to [[language]], but also [[mimesis]].<ref>Mimesis in modern academic writing, starting with [[Erich Auerbach]], is a technical word, which is not necessarily exactly the same in meaning as the original Greek.</ref> They describe the ability to create language as part of an internal modeling of [[reality]], and specific to humankind. Other results are [[consciousness]], and [[imagination]] or [[fantasy]]. Modern proponents of a genetic predisposition to language itself include [[Noam Chomsky]] and [[Steven Pinker]].

If reason is symbolic thinking, and peculiarly human, then this implies that humans have a special ability to maintain a clear consciousness of the distinctness of "icons" or images and the real things they represent. Merlin Donald writes:<ref name=MerlinDonald>{{cite book|first=Merlin|last=Donald|title=Origins of the Modern Mind}}{{ISBN?}}</ref>{{rp|172}}
<blockquote>A dog might perceive the "meaning" of a fight that was realistically play-acted by humans, but it could not reconstruct the message or distinguish the representation from its referent (a real fight).... Trained apes are able to make this distinction; young children make this distinction early—hence, their effortless distinction between play-acting an event and the event itself</blockquote>

In classical descriptions, an equivalent description of this mental faculty is {{transliteration|grc|eikasia}}, in the philosophy of Plato.<ref name=KleinMeno>{{cite book|first=Jacob|last=Klein|title=A Commentary on the [[Meno]]}}</ref>{{rp|at=Ch.5}} This is the ability to perceive whether a perception is an image of something else, related somehow but not the same, and therefore allows humans to perceive that a dream or memory or a reflection in a mirror is not reality as such. What Klein refers to as {{transliteration|grc|dianoetic eikasia}} is the {{transliteration|grc|eikasia}} concerned specifically with thinking and mental images, such as those mental symbols, icons, ''{{lang|en-emodeng|signes}}'', and marks discussed above as definitive of reason. Explaining reason from this direction: human thinking is special in that we often understand visible things as if they were themselves images of our intelligible "objects of thought" as "foundations" ({{transliteration|grc|hypothēses}} in Ancient Greek). This thinking ({{transliteration|grc|dianoia}}) is "...an activity which consists in making the vast and diffuse jungle of the visible world depend on a plurality of more 'precise' {{transliteration|grc|noēta}}".{{r|KleinMeno|page=122}}

Both Merlin Donald and the Socratic authors such as Plato and Aristotle emphasize the importance of {{transliteration|grc|mimēsis}}, often translated as ''imitation'' or ''representation''. Donald writes:{{r|MerlinDonald|page=169}}
<blockquote>Imitation is found especially in monkeys and apes [...but...] Mimesis is fundamentally different from imitation and mimicry in that it involves the invention of intentional representations.... Mimesis is not absolutely tied to external communication.</blockquote>

{{transliteration|grc|Mimēsis}} is a concept, now popular again in academic discussion, that was particularly prevalent in Plato's works. In Aristotle, it is discussed mainly in the ''[[Poetics (Aristotle)|Poetics]]''. In Michael Davis's account of the theory of man in that work:<ref>{{cite book|chapter=Introduction|title=[[Poetics (Aristotle)|Poetics]] of Aristotle|last1=Davis|first1=Michael|first2=Seth|last2=Benardete|pages=xvii, xxviii}}</ref>
<blockquote>It is the distinctive feature of human action, that whenever we choose what we do, we imagine an action for ourselves as though we were inspecting it from the outside. Intentions are nothing more than imagined actions, internalizings of the external. All action is therefore imitation of action; it is poetic...<ref>Davis uses "poetic" in an unusual sense, questioning the contrast in Aristotle between action ({{transliteration|grc|praxis}}, the {{transliteration|grc|praktikē}}) and making ({{transliteration|grc|poēsis}}, the {{transliteration|grc|poētikē}}): "Human [peculiarly human] action is imitation of action because thinking is always rethinking. Aristotle can define human beings as at once rational animals, political animals, and imitative animals because in the end the three are the same."</ref></blockquote>

Donald, like Plato (and Aristotle, especially in ''[[On Memory|On Memory and Recollection]]''), emphasizes the peculiarity in humans of voluntary initiation of a search through one's mental world. The ancient Greek {{transliteration|grc|anamnēsis}}, normally translated as "recollection" was opposed to {{transliteration|grc|mneme}} or "memory". Memory, shared with some animals,<ref>{{cite book|author=Aristotle|title=[[On Memory]]|at=450a 15–16}}</ref> requires a consciousness not only of what happened in the past, but also ''that'' something happened in the past, which is in other words a kind of {{transliteration|grc|eikasia}}{{r|KleinMeno|page=109}} "...but nothing except man is able to recollect."<ref>{{cite book|author=Aristotle|title=[[History of Animals]]|at=I.1.488b.25–26}}</ref> Recollection is a deliberate effort to search for and recapture something once known. Klein writes that, "To become aware of our having forgotten something means to begin recollecting."{{r|KleinMeno|page=112}} Donald calls the same thing ''autocueing'', which he explains as follows:{{r|MerlinDonald|page=173}}<ref>{{cite book|last=Donald|first=Merlin|title=A Mind So Rare|pages=140–141}}{{ISBN?}}</ref> "Mimetic acts are reproducible on the basis of internal, self-generated cues. This permits voluntary recall of mimetic representations, without the aid of external cues—probably the earliest form of representational ''thinking''."

In a celebrated paper, the fantasy author and philologist [[J.R.R. Tolkien]] wrote in his essay "On Fairy Stories" that the terms "fantasy" and "enchantment" are connected to not only "the satisfaction of certain primordial human desires" but also "the origin of language and of the mind".{{cite quote|date=September 2023}}

===Logical reasoning methods and argumentation===
{{main|Logical reasoning}}
A subdivision of [[philosophy]] and a variety of reasoning is [[logic]]. The traditional main division made in philosophy is between [[deductive reasoning]] and [[inductive reasoning]]. [[Logic|Formal logic]] has been described as ''the science of deduction''.<ref>{{cite book|last=Jeffrey|first=Richard|year=1991|title=Formal logic: its scope and limits|edition=3rd|location=New York|publisher=McGraw-Hill|page=1}}</ref> The study of inductive reasoning is generally carried out within the field known as [[informal logic]] or [[critical thinking]].

====Deductive reasoning====
{{Main|Deductive reasoning}}
Deduction is a form of reasoning in which a conclusion follows necessarily from the stated premises. A deduction is also the name for the conclusion reached by a deductive reasoning process. A classic example of deductive reasoning is evident in [[syllogism]]s like the following:
{| {{Table}}
! Premise 1
| All humans are mortal.
|-
! Premise 2 
| Socrates is a human.
|-
! Conclusion 
| Socrates is mortal.
|}
The reasoning in this argument is deductively [[Validity (logic)|valid]] because there is no way in which both premises could be true and the conclusion be false.

====Inductive reasoning====
{{Main|Inductive reasoning}}
Induction is a form of inference that produces [[category of being|properties or relations]] about unobserved objects or [[type (metaphysics)|types]] based on [[event (philosophy)|previous observations or experiences]], or that formulates general statements or [[law (principle)|laws]] based on limited observations of recurring [[phenomena]]l patterns.

Inductive reasoning contrasts with deductive reasoning in that, even in the strongest cases of inductive reasoning, the truth of the premises does not guarantee the truth of the conclusion. Instead, the conclusion of an inductive argument follows with some degree of [[probability]]. For this reason also, the conclusion of an inductive argument contains more information than is already contained in the premises. Thus, this method of reasoning is ampliative.

A classic example of inductive reasoning comes from the [[empiricist]] [[David Hume]]:
{| {{Table}}
! Premise
| The sun has risen in the east every morning up until now.
|-
! Conclusion 
| The sun will also rise in the east tomorrow.
|}

====Analogical reasoning====
{{Main|Analogical reasoning}}
Analogical reasoning is a form of inductive reasoning from a particular to a particular. It is often used in [[case-based reasoning]], especially legal reasoning.<ref>{{cite book |last=Walton |first=Douglas N. |title=Systematic Approaches to Argument by Analogy |chapter=Argumentation Schemes for Argument from Analogy |author-link=Douglas N. Walton |date=2014 |editor-last=Ribeiro |editor-first=Henrique Jales |series=Argumentation library |volume=25 |location=Cham; New York |publisher=[[Springer Verlag]] |pages=23–40 |isbn=978-3319063331 |oclc=884441074 |doi=10.1007/978-3-319-06334-8_2|chapter-url=https://scholar.uwindsor.ca/crrarpub/15 }}</ref> An example follows:
{| {{Table}}
! Premise 1
| Socrates is human and mortal.
|-
! Premise 2
| Plato is human.
|-
! Conclusion 
| Plato is mortal.
|}

Analogical reasoning is a weaker form of inductive reasoning from a single example, because inductive reasoning typically uses a large number of examples to reason from the particular to the general.<ref>{{cite encyclopedia |last=Henderson |first=Leah |title=The Problem of Induction |encyclopedia= The Stanford Encyclopedia of Philosophy |year=2022 |url=http://plato.stanford.edu/entries/induction-problem/ |publisher=Metaphysics Research Lab, Stanford University }}</ref> Analogical reasoning often leads to wrong conclusions. For example:
{| {{Table}}
! Premise 1
| Socrates is human and male.
|-
! Premise 2
| [[Ada Lovelace]] is human.
|-
! Conclusion 
| Ada Lovelace is male.
|}

====Abductive reasoning====
{{Main|Abductive reasoning}}
Abductive reasoning, or argument to the best explanation, is a form of reasoning that does not fit in either the deductive or inductive categories, since it starts with incomplete set of observations and proceeds with likely possible explanations. The conclusion in an abductive argument does not follow with certainty from its premises and concerns something unobserved. What distinguishes abduction from the other forms of reasoning is an attempt to favour one conclusion above others, by subjective judgement or by attempting to falsify alternative explanations or by demonstrating the likelihood of the favoured conclusion, given a set of more or less disputable assumptions. For example, when a patient displays certain symptoms, there might be various possible causes, but one of these is preferred above others as being more probable.

====Fallacious reasoning====
{{Main|Fallacy|Formal fallacy|Informal fallacy}}
Flawed reasoning in arguments is known as [[fallacy|fallacious reasoning]]. Bad reasoning within arguments can result from either a [[formal fallacy]] or an [[informal fallacy]].

Formal fallacies occur when there is a problem with the form, or structure, of the argument. The word "formal" refers to this link to the ''form'' of the argument. An argument that contains a formal fallacy will always be invalid.

An informal fallacy is an error in reasoning that occurs due to a problem with the ''content'', rather than the form or structure, of the argument.

===Unreasonable decisions and actions===
In law relating to the actions of an employer or a [[public body]], a decision or action which falls outside the range of actions or decision available when acting in good faith can be described as "unreasonable". Use of the term is considered in the [[English law]] cases of ''[[Thomas Warrington, 1st Baron Warrington of Clyffe#Judgements|Short v Poole Corporation]]'' (1926), ''[[Associated Provincial Picture Houses Ltd v Wednesbury Corporation]]'' (1947) and ''Braganza v BP Shipping Limited'' (2015).<ref>{{Cite web|url=http://www.bailii.org/uk/cases/UKSC/2015/17.html|title=Braganza v BP Shipping Ltd [2015] UKSC 17 (18 March 2015)}|access-date=28 May 2024}}</ref>

==Traditional problems raised concerning reason==
Philosophy is often characterized as a pursuit of rational understanding, entailing a more rigorous and dedicated application of human reasoning than commonly employed. Philosophers have long debated two fundamental questions regarding reason, essentially examining reasoning itself as a human endeavor, or philosophizing about philosophizing. The first question delves into whether we can place our trust in reason's ability to attain [[knowledge]] and [[truth]] more effectively than alternative methods. The second question explores whether a life guided by reason, a life that aims to be guided by reason, can be expected to lead to greater [[eudaimonia|happiness]] compared to other approaches to life.

===Reason versus truth, and "first principles"===
{{See also|Truth|First principle|Nous}}
Since [[classical antiquity]] a question has remained constant in philosophical debate (sometimes seen as a conflict between [[Platonism]] and [[Aristotelianism]]) concerning the role of reason in confirming [[truth]]. People use logic, [[deductive reasoning|deduction]], and [[inductive reasoning|induction]] to reach conclusions they think are true. Conclusions reached in this way are considered, according to Aristotle, more certain than sense perceptions on their own.<ref>{{cite book|author=Aristotle|title=[[Metaphysics (Aristotle)|Metaphysics]]|at=[https://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A1999.01.0051%3Abook%3D1%3Asection%3D981b 981b]|language=grc|quote=τὴν ὀνομαζομένην σοφίαν περὶ τὰ πρῶτα αἴτια καὶ τὰς ἀρχὰς ὑπολαμβάνουσι πάντες: ὥστε, καθάπερ εἴρηται πρότερον, ὁ μὲν ἔμπειρος τῶν ὁποιανοῦν ἐχόντων αἴσθησιν εἶναι δοκεῖ σοφώτερος, ὁ δὲ τεχνίτης τῶν ἐμπείρων, χειροτέχνου δὲ ἀρχιτέκτων, αἱ δὲ θεωρητικαὶ τῶν ποιητικῶν μᾶλλον.|trans-quote=...what is called Wisdom is concerned with the primary causes and principles, so that, as has been already stated, the man of experience is held to be wiser than the mere possessors of any power of sensation, the artist than the man of experience, the master craftsman than the artisan; and the speculative sciences to be more learned than the productive.}}</ref> On the other hand, if such reasoned conclusions are only built originally upon a foundation of sense perceptions, then our most logical conclusions can never be said to be certain because they are built upon the very same fallible perceptions they seek to better.<ref>{{cite book|author=Aristotle|title=[[Metaphysics (Aristotle)|Metaphysics]]|at=[https://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A1999.01.0051%3Abook%3D1%3Asection%3D1009b 1009b]|language=grc|quote=ποῖα οὖν τούτων ἀληθῆ ἢ ψευδῆ, ἄδηλον: οὐθὲν γὰρ μᾶλλον τάδε ἢ τάδε ἀληθῆ, ἀλλ᾽ ὁμοίως. διὸ Δημόκριτός γέ φησιν ἤτοι οὐθὲν εἶναι ἀληθὲς ἢ ἡμῖν γ᾽ ἄδηλον.|trans-quote=Thus it is uncertain which of these impressions are true or false; for one kind is no more true than another, but equally so. And hence Democritus says that either there is no truth or we cannot discover it.}}</ref>

This leads to the question of what types of [[first principles]], or starting points of reasoning, are available for someone seeking to come to true conclusions. In Greek, "[[first principles]]" are {{transliteration|grc|[[Arche|archai]]}}, "starting points",<ref>{{cite book|author=Aristotle|title=[[Metaphysics (Aristotle)|Metaphysics]]|at=[https://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A1999.01.0051%3Abook%3D1%3Asection%3D983a 983a]|language=grc|quote=ἐπεὶ δὲ φανερὸν ὅτι τῶν ἐξ ''ἀρχῆς'' αἰτίων δεῖ λαβεῖν ''ἐπιστήμην'' (τότε γὰρ εἰδέναι φαμὲν ἕκαστον, ὅταν τὴν ''πρώτην'' αἰτίαν οἰώμεθα ''γνωρίζειν'')|trans-quote=It is clear that we must obtain knowledge of the ''primary'' causes, because it is when we think that we understand its ''primary'' cause that we claim to ''know'' each particular thing.}}</ref> and the faculty used to perceive them is sometimes referred to in Aristotle<ref>{{cite book|author=Aristotle|title=[[Nicomachean Ethics]]|at=[https://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A1999.01.0053%3Abekker+page%3D1139a 1139b]|language=grc|quote=ἀμφοτέρων δὴ τῶν ''νοητικῶν'' μορίων ἀλήθεια τὸ ἔργον. καθ᾽ ἃς οὖν μάλιστα ἕξεις ἀληθεύσει ἑκάτερον, αὗται ἀρεταὶ ἀμφοῖν|trans-quote=The attainment of truth is then the function of both the ''intellectual'' parts of the soul. Therefore their respective virtues are those dispositions that will best qualify them to attain truth.}}</ref> and Plato<ref>{{cite book|author=Plato|title=[[Republic (Plato)|Republic]]|at=[https://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A1999.01.0167%3Abook%3D6%3Asection%3D490b 490b]|language=grc|quote=μιγεὶς τῷ ὄντι ὄντως, γεννήσας νοῦν καὶ ἀλήθειαν, γνοίη|trans-quote=Consorting with reality really, he would beget intelligence and truth, attain to knowledge}}</ref> as {{transliteration|grc|[[nous]]}} which was close in meaning to ''awareness'' or ''[[consciousness]]''.<ref name=StraussProgress>{{cite book|quote=This quest for the beginnings proceeds through sense perception, reasoning, and what they call ''noesis'', which is literally translated by 'understanding' or 'intellect,' and which we can perhaps translate a little bit more cautiously by 'awareness,' an awareness of the mind's eye as distinguished from sensible awareness.|chapter=Progress or Return|title=An Introduction to Political Philosophy: Ten Essays by Leo Strauss|first=Leo|last=Strauss|author-link=Leo Strauss|orig-year=1975|editor-first=Hilail|editor-last=Gilden|location=Detroit|publisher=Wayne State University Press|year=1989}}</ref>

[[Empiricism]] (sometimes associated with Aristotle<ref>However, the empiricism of Aristotle must certainly be doubted. For example in ''Metaphysics'' 1009b, cited above, he criticizes people who think knowledge might not be possible because, "They say that the impression given through sense-perception is necessarily true; for it is on these grounds that both [[Empedocles]] and Democritus and practically all the rest have become obsessed by such opinions as these."</ref> but more correctly associated with [[Great Britain|British]] philosophers such as [[John Locke]] and [[David Hume]], as well as their ancient equivalents such as [[Democritus]]) asserts that sensory impressions are the only available starting points for reasoning and attempting to attain truth. This approach always leads to the controversial conclusion that [[absolute knowledge]] is not attainable. [[Idealism]], (associated with Plato and his school), claims that there is a "higher" reality, within which certain people can directly discover truth without needing to rely only upon the senses, and that this higher reality is therefore the primary source of truth.

Philosophers such as [[Plato]], [[Aristotle]], [[Al-Farabi]], [[Avicenna]], [[Averroes]], [[Maimonides]], [[Aquinas]], and [[Hegel]]  argued that reason must be fixed and discoverable—perhaps by dialectic, analysis, or study. Religious philosophers such as [[Thomas Aquinas]] and [[Étienne Gilson]] attempted to show that reason and [[revelation]] are compatible. According to Hegel, "...the only thought which Philosophy brings with it to the contemplation of [[History]], is the simple conception of reason; that reason is the Sovereign of the World; that the history of the world, therefore, presents us with a rational process."<ref>{{cite book|first=G.W.F.|last=Hegel|title=[[Lectures on the Philosophy of History|''The Philosophy of History'']]|page=9|publisher=Dover Publications Inc.|isbn=0486201120|year=1956|orig-year=1837}}</ref>

Since the 17th century [[rationalist]]s, reason has often been taken to be a [[subjectivity|subjective faculty]], or rather the unaided ability ([[pure reason]]) to form concepts. For [[Descartes]], [[Spinoza]], and [[Gottfried Wilhelm Leibniz|Leibniz]], this was associated with [[mathematics]]. [[Immanuel Kant|Kant]] attempted to show that pure reason could form concepts ([[time]] and [[space]]) that are the conditions of experience. Kant made his argument in opposition to Hume, who denied that reason had any role to play in experience.

===Reason versus emotion or passion===
{{See also|Emotion|Passion (emotion)}}
After Plato and Aristotle, [[western literature]] often treated reason as being the faculty that trained the passions and appetites.{{citation needed|date=August 2016}} [[Stoic philosophy]], by contrast, claimed most emotions were merely false judgements.<ref name=":0">{{Cite book|last=Sharples|first=R. W.|title=The Oxford companion to philosophy|date=2005|publisher=Oxford University Press|others=Ted Honderich|isbn=978-0191532658|edition=2nd|location=Oxford|page=896|oclc=62563098|quote=Moral virtue is the only good an wickedness the only evil... Emotions are interpreted in intellectual terms; those such as distress, pity (which is a species of distress), and fear which reflect false judgements about what is evil, are to be avoided (as also are those which reflect false judgement about what is good, such as love of honours or riches)... They did however allow the wise man such 'good feelings' as 'watchfulness' or kindness the difference being that these are based on sound (Stoic) reasoning concerning what matters and what does not.}}</ref><ref name=":1">{{Cite book|last=Rufus|first=Musonius|title=Concise Routledge encyclopedia of philosophy|date=2000|publisher=Routledge|others=Routledge|isbn=0203169948|location=London|page=863|oclc=49569365|quote=Vice is founded on 'passions': these are at root false value judgements, in which we lose rational control by overvaluing things which are in fact indifferent. Virtue, a set of sciences governing moral choice, is the one thing of intrinsic worth and therefore genuinely 'good'.}}</ref> According to the Stoics the only good is virtue, and the only evil is vice, therefore emotions that judged things other than vice to be bad (such as fear or distress), or things other than virtue to be good (such as greed) were simply false judgements and should be discarded (though positive emotions based on true judgements, such as kindness, were acceptable).<ref name=":0" /><ref name=":1" /><ref>{{Citation|last=Baltzly|first=Dirk|title=Stoicism|date=2018|url=https://plato.stanford.edu/archives/spr2019/entries/stoicism/|encyclopedia=The Stanford Encyclopedia of Philosophy|editor-last=Zalta|editor-first=Edward N.|edition=Spring 2019|publisher=Metaphysics Research Lab, Stanford University|access-date=2021-03-27}}</ref> After the critiques of reason in the early Enlightenment the appetites were rarely discussed or were conflated with the passions.{{citation needed|date=August 2016}} Some Enlightenment camps took after the Stoics to say reason should oppose passion rather than order it, while others like the Romantics believed that passion displaces reason, as in the maxim "follow your heart".{{citation needed|date=August 2016}}

Reason has been seen as cold, an "enemy of mystery and ambiguity",<ref name="Radford and Frazier (2017)">{{cite journal|author-link1=Benjamin Radford|last1=Radford|first1=Benjamin|author-link2=Kendrick Frazier|last2=Frazier|first2=Kendrick|title=The Edge of Reason: A Rational Skeptic in an Irrational World |journal=Skeptical Inquirer |date=January 2017 |volume=41 |issue=1 |page=60}}</ref> a slave, or judge, of the passions, notably in the work of [[David Hume]]. More recently, [[Freud]] wrote, “It seems as though the activity of the other agencies of the mind is able only to modify the pleasure principle but not to nullify it; and it remains a question of the greatest theoretical importance, and one that has not yet been answered, when and how it is ever possible for the pleasure principle to be overcome.” <ref>{{cite book |last=Freud|first=Sigmund |date=1959 |title=An Outline of Psycho-Analysis |publisher= London: Hogarth Press|url= https://archive.org/details/b2981487x/page/n5/mode/1up }}</ref>

Reasoning that claims the object of a desire is demanded by logic alone is called ''[[Rationalization (making excuses)|rationalization]]''.{{citation needed|date=August 2016}}

[[Rousseau]] first proposed, in his second ''[[Discourse on Inequality|Discourse]]'', that reason and political life is not natural and is possibly harmful to mankind.<ref>{{Citation|last=Velkley|first=Richard|chapter=Speech. Imagination, Origins: Rousseau and the Political Animal|title=Being after Rousseau: Philosophy and Culture in Question|year=2002|publisher=University of Chicago Press}}</ref> He asked what really can be said about what is natural to mankind. What, other than reason and civil society, "best suits his constitution"? Rousseau saw "two principles prior to reason" in human nature. First we hold an intense interest in our own well-being. Secondly we object to the suffering or death of any sentient being, especially one like ourselves.<ref>{{Citation|last=Rousseau|first=Jean-Jacques|chapter=Preface|title=Discourse on the Origin and Foundations of Inequality Among Men or Second Discourse|publisher=Cambridge University Press|editor=Gourevitch|year=1997|orig-year=1755}}</ref> These two passions lead us to desire more than we could achieve. We become dependent upon each other, and on relationships of authority and obedience. This effectively puts the human race into slavery. Rousseau says that he almost dares to assert that nature does not destine men to be healthy. According to [[Richard Velkley]], "Rousseau outlines certain programs of rational self-correction, most notably the political legislation of the ''[[The Social Contract|Contrat Social]]'' and the moral education in ''[[Emile: or, On Education|Émile]]''. All the same, Rousseau understands such corrections to be only ameliorations of an essentially unsatisfactory condition, that of socially and intellectually corrupted humanity."{{cite quote|date=September 2023}}

This quandary presented by Rousseau led to [[Immanuel Kant|Kant]]'s new way of justifying reason as freedom to create good and evil. These therefore are not to be blamed on nature or God. In various ways, [[German Idealism]] after Kant, and major later figures such [[Nietzsche]], [[Bergson]], [[Husserl]], [[Max Scheler|Scheler]], and [[Heidegger]], remain preoccupied with problems coming from the metaphysical demands or urges of reason.<ref>{{Citation|last=Velkley|first=Richard|chapter=Freedom, Teleology, and Justification of Reason|title=Being after Rousseau: Philosophy and Culture in Question|year=2002|publisher=University of Chicago Press}}</ref> Rousseau and these later writers also exerted a large influence on art and politics. Many writers (such as [[Nikos Kazantzakis]]) extol passion and disparage reason. In politics modern [[nationalism]] comes from Rousseau's argument that rationalist [[cosmopolitanism]] brings man ever further from his natural state.<ref>{{Citation|chapter=Rousseau and the Origins of Nationalism|last=Plattner|first=Marc|year=1997|publisher=University of Chicago Press|title=The Legacy of Rousseau}}</ref>

In ''[[Descartes' Error]]'', [[Antonio Damasio]] presents the "[[Somatic marker hypothesis|Somatic Marker Hypothesis]]" which states that emotions guide behavior and decision-making. Damasio argues that these somatic markers (known collectively as "gut feelings") are "intuitive signals" that direct our decision making processes in a certain way that cannot be solved with rationality alone. Damasio further argues that rationality requires emotional input in order to function.

===Reason versus faith or tradition===
{{Main|Faith|Religion|Tradition}}
There are many religious traditions, some of which are explicitly [[Fideism|fideist]] and others of which claim varying degrees of [[rationalism]]. Secular critics sometimes accuse all religious adherents of irrationality; they claim such adherents are guilty of ignoring, suppressing, or forbidding some kinds of reasoning concerning some subjects (such as religious dogmas, moral taboos, etc.).<ref>{{Cite book|title=The God Delusion|last=Dawkins|first=Richard|year=2008|publisher=Mariner Books|isbn=978-0618918249|edition=Reprint|language=en|quote=Scientists... see the fight for evolution as only one battle in a larger war: a looming war between supernaturalism on the one side and rationality on the other.|url=https://archive.org/details/goddelusion00dawk_0}}</ref> Though [[theology|theologies]] and [[religion]]s such as [[Monotheism|classical monotheism]] typically do not admit to being [[irrationality|irrational]], there is often a perceived conflict or tension between [[faith]] and [[tradition]] on the one hand, and reason on the other, as potentially competing sources of [[wisdom]], [[law]], and [[truth]].{{r|StraussProgress}}<ref>{{cite book|first=John|last=Locke|chapter=Of Faith and Reason, and their distinct provinces|year=1689|chapter-url=https://archive.org/details/in.ernet.dli.2015.223061/page/n601/mode/2up|title=An Essay concerning Human Understanding|volume=IV}}</ref>

Religious adherents sometimes respond by arguing that faith and reason can be reconciled, or have different non-overlapping domains, or that critics engage in a similar kind of irrationalism:
; Reconciliation : Philosopher [[Alvin Plantinga]] argues that there is no real conflict between reason and [[classical theism]] because classical theism explains (among other things) why the universe is intelligible and why reason can successfully grasp it.<ref>{{multiref2
|1={{Cite book|title=Where the Conflict Really Lies: Science, Religion, and Naturalism|last=Plantinga|first=Alvin|year=2011|publisher=Oxford University Press|isbn=978-0199812097|edition=1|language=en}}
|2={{Cite book|title=Natural Signs and Knowledge of God: A New Look at Theistic Arguments|year=2012|publisher=Oxford University Press|isbn=978-0199661077|edition=Reprint|location=Oxford|language=en}}
}}</ref>
; Non-overlapping magisteria : Evolutionary biologist [[Stephen Jay Gould]] argues that there need not be conflict between reason and religious belief because they are each authoritative in their own domain (or "magisterium").<ref>{{multiref2
|1={{Cite web|url=http://www.stephenjaygould.org/library/gould_noma.html|url-status=usurped|archive-url=https://web.archive.org/web/20160425013318/http://www.stephenjaygould.org/library/gould_noma.html|archive-date=2016-04-25|title=Nonoverlapping Magisteria|author=[[Stephen Jay Gould]] |date=1997|website=www.stephenjaygould.org|access-date=2016-04-06|quote=To say it for all my colleagues and for the umpteenth millionth time (from college bull sessions to learned treatises): science simply cannot (by its legitimate methods) adjudicate the issue of God's possible superintendence of nature. We neither affirm nor deny it; we simply can't comment on it as scientists.}}
|2={{Cite book|title=The God Delusion|last=Dawkins|first=Richard|year=2008|publisher=Mariner Books|isbn=978-0618918249|edition=Reprint|language=en|chapter=4|quote=This sounds terrific, right up until you give it a moment's thought. You then realize that the presence of a creative deity in the universe is clearly a scientific hypothesis. Indeed, it is hard to imagine a more momentous hypothesis in all of science. A universe with a god would be a completely different kind of universe from one without, and it would be a scientific difference. God could clinch the matter in his favour at any moment by staging a spectacular demonstration of his powers, one that would satisfy the exacting standards of science. Even the infamous Templeton Foundation recognized that God is a scientific hypothesis—by funding double-blind trials to test whether remote prayer would speed the recovery of heart patients. It didn't, of course, although a control group who knew they had been prayed for tended to get worse (how about a class action suit against the Templeton Foundation?) Despite such well-financed efforts, no evidence for God's existence has yet appeared.|chapter-url=https://archive.org/details/goddelusion00dawk_0|url-access=registration|url=https://archive.org/details/goddelusion00dawk_0}}
}}</ref> If so, reason can work on those problems over which it has authority while other sources of knowledge or opinion can have authority on the big questions.<ref>{{Cite journal|url=https://www.pdcnet.org/pdc/bvdb.nsf/purchase?openform&fp=philo&id=philo_2009_0012_0001_0005_0023|url-access=subscription|title=The Meaning of Life as Narrative: A New Proposal for Interpreting Philosophy's 'Primary' Question|first=Joshua W.|last=Seachris|journal=Philo|access-date=2016-04-06|date=April 2009|volume=12|issue=1|pages=5–23|doi=10.5840/philo20091211}}</ref>
; {{lang|la|[[Tu quoque]]}} : Philosophers [[Alasdair MacIntyre]] and [[Charles Taylor (philosopher)|Charles Taylor]] argue that those critics of traditional religion who are adherents of [[Secularity|secular]] [[liberalism]] are also sometimes guilty of ignoring, suppressing, and forbidding some kinds of reasoning about subjects.<ref>{{multiref2
|1={{Cite book|title=Three Rival Versions of Moral Enquiry: Encyclopaedia, Genealogy, and Tradition|year=1991|publisher=University of Notre Dame Press|isbn=978-0268018771|edition=60067th|language=en}}
|2={{Cite book|title=A Secular Age|last=Taylor|first=Charles|year=2007|publisher=The Belknap Press of Harvard University Press|isbn=978-0674026766|edition=1st|language=en}}
}}</ref> Similarly, philosophers of science such as [[Paul Feyerabend|Paul Feyarabend]] argue that scientists sometimes ignore or suppress evidence contrary to the dominant [[paradigm]].
; Unification : Theologian Joseph Ratzinger, later [[Benedict XVI]], asserted that "Christianity has understood itself as the religion of the Logos, as the religion according to reason," referring to {{Bibleverse|John|1}} {{lang|la|Ἐν ἀρχῇ ἦν ὁ λόγος}}, usually translated as "In the beginning was the Word (Logos)." Thus, he said that the Christian faith is "open to all that is truly rational", and that the rationality of Western Enlightenment "is of Christian origin".<ref>{{Cite web | first=Joseph|last=Ratzinger|url=http://www.catholiceducation.org/en/culture/catholic-contributions/cardinal-ratzinger-on-europe-s-crisis-of-culture.html | title=Cardinal Ratzinger on Europe's Crisis of Culture|year=2005}}</ref>

Some commentators have claimed that [[Western culture|Western civilization]] can be almost defined by its serious testing of the limits of tension between "unaided" reason and [[faith]] in "[[revelation|revealed]]" truths—figuratively summarized as [[Athens]] and [[Jerusalem]], respectively.<ref>{{multiref2
|1={{Cite book|last=Reynolds |first=John Mark|title=When Athens Met Jerusalem: An Introduction to Classical and Christian Thought|year=2009|publisher=IVP Academic|isbn=978-0830829231|publication-place=Downers Grove, Ill.|language=en}}
|2={{Cite journal|title=Athens and/or Jerusalem|journal=Annals of the New York Academy of Sciences|volume=950|issue=1|page=17|last=Pelikan|first=Jaroslav|year=2001|bibcode=2001NYASA.950...17P|doi=10.1111/j.1749-6632.2001.tb02124.x|s2cid=21347905}}
}}</ref> [[Leo Strauss]] spoke of a "Greater [[Western world|West]]" that included all areas under the influence of the tension between Greek rationalism and [[Abrahamic]] revelation, including the [[Muslim]] lands. He was particularly influenced by the [[Islamic philosophy|Muslim philosopher]] [[Farabi|Al-Farabi]]. To consider to what extent [[Eastern philosophy]] might have partaken of these important tensions, Strauss thought it best to consider whether [[dharma]] or [[tao]] may be equivalent to [[Nature (philosophy)|Nature]] ({{transliteration|grc|[[physis]]}} in Greek). According to Strauss the beginning of philosophy involved the "discovery or invention of nature" and the "pre-philosophical equivalent of nature" was supplied by "such notions as 'custom' or 'ways{{'"}}, which appear to be really universal in all times and places. The philosophical concept of nature or natures as a way of understanding {{transliteration|grc|archai}} (first principles of knowledge) brought about a peculiar tension between reasoning on the one hand, and tradition or faith on the other.{{r|StraussProgress}}

==Reason in particular fields of study==

===Psychology and cognitive science===
{{See also|Psychology of reasoning}}
Scientific research into reasoning is carried out within the fields of [[psychology]] and [[cognitive science]]. Psychologists attempt to determine whether or not people are capable of rational thought in a number of different circumstances.

Assessing how well someone engages in reasoning is the project of determining the extent to which the person is [[Rationality|rational]] or acts rationally. It is a key research question in the [[psychology of reasoning]] and cognitive science of reasoning. [[Rationality]] is often divided into its respective [[Rationality#Theoretical and practical|theoretical and practical counterparts]].

====Behavioral experiments on human reasoning====
Experimental cognitive psychologists research reasoning behaviour. Such research may focus, for example, on how people perform on tests of reasoning such as [[Intelligence tests|intelligence]] or [[IQ]] tests, or on how well people's reasoning matches ideals set by logic (see, for example, the [[Wason test]]).<ref>{{cite book|last=Manktelow|first=K.I.|year=1999|title=Reasoning and Thinking (Cognitive Psychology: Modular Course)|location=Hove, Sussex|publisher=Psychology Press}}</ref> Experiments examine how people make inferences from conditionals like ''if A then B'' and how they make inferences about alternatives like ''A or else B''.<ref>{{cite book|last1=Johnson-Laird|first1=P.N.|last2=Byrne|first2=R.M.J.|year=1991|title=Deduction|location=Hillsdale|publisher=Erlbaum}}</ref> They test whether people can make valid deductions about spatial and temporal relations like ''A is to the left of B'' or ''A happens after B'', and about quantified assertions like ''all the A are B''.<ref>{{cite book|last1=Johnson-Laird|first1=P.N.|year=2006|title=How we reason|location=Oxford|publisher=Oxford University Press}}</ref> Experiments investigate how people make inferences about factual situations, hypothetical possibilities, probabilities, and [[counterfactual thinking|counterfactual]] situations.<ref>{{cite book|last=Byrne|first=R.M.J.|year=2005|title=The Rational Imagination: How People Create Counterfactual Alternatives to Reality|location=Cambridge, Mass.|publisher=MIT Press}}</ref>

====Developmental studies of children's reasoning====
Developmental psychologists investigate the development of reasoning from birth to adulthood. Piaget's [[theory of cognitive development]] was the first complete theory of reasoning development. Subsequently, several alternative theories were proposed, including the [[neo-Piagetian theories of cognitive development]].<ref>{{cite book|last=Demetriou|first=A.|year=1998|chapter=Cognitive development|editor-first1=A.|editor-last1=Demetriou|editor-first2=W.|editor-last2=Doise|editor-first3=K.F.M.|editor-last3=van Lieshout|title=Life-span developmental psychology|pages=179–269|location=London|publisher=Wiley}}</ref>

====Neuroscience of reasoning====
The biological functioning of the brain is studied by [[neurophysiologist]]s, [[Cognitive neuroscience|cognitive neuroscientists]], and [[neuropsychologist]]s. This includes research into the structure and function of normally functioning brains, as well as of damaged or otherwise unusual brains. In addition to carrying out research into reasoning, some psychologists—for example [[clinical psychologist]]s and [[psychotherapists]]—work to alter people's reasoning habits when those habits are unhelpful.<ref>{{Cite journal |last1=Goel |first1=Vinod |last2=Navarrete |first2=Gorka |last3=Noveck |first3=Ira A. |last4=Prado |first4=Jérôme |year=2017 |title=Editorial: The Reasoning Brain: The Interplay between Cognitive Neuroscience and Theories of Reasoning |journal=Frontiers in Human Neuroscience |volume=10 |pages=673 |doi=10.3389/fnhum.2016.00673|doi-access=free |pmid=28105010 |pmc=5214378 }}</ref>

===Computer science===

====Automated reasoning====
{{Main|Automated reasoning|Computational logic}}
{{see also|Reasoning system|Case-based reasoning|Semantic reasoner|Knowledge reasoning}}
In [[artificial intelligence]] and [[computer science]], scientists study and use [[automated reasoning]] for diverse applications including [[automated theorem proving]] the [[formal semantics of programming languages]], and [[formal specification]] in [[software engineering]].

====Meta-reasoning====
{{See also|Metacognition}}
'''Meta-reasoning'''<!--boldface per [[WP:R#PLA]]--> is reasoning about reasoning. In computer science, a system performs meta-reasoning when reasoning about its operation.<ref>{{citation|year=2002|volume=2408/2002|issue=65|first=Stefania |last=Costantini |title=Computational Logic: Logic Programming and Beyond |chapter=Meta-reasoning: A Survey |series=Lecture Notes in Computer Science |doi=10.1007/3-540-45632-5_11 |pages=253–288|isbn=978-3540439608}}</ref> This requires a programming language capable of [[reflection (computer science)|reflection]], the ability to observe and modify its own structure and behaviour.

===Evolution of reason===
[[File:Capuchin monkeys sharing.jpg|thumb| Dan Sperber believes that reasoning in groups is more effective and promotes their evolutionary fitness.]]
A species could benefit greatly from better abilities to reason about, predict, and understand the world. French social and cognitive scientists [[Dan Sperber]] and Hugo Mercier argue that, aside from these benefits, other forces could have been driving the evolution of reason. They point out that reasoning is very difficult for humans to do effectively, and that it is hard for individuals to doubt their own beliefs ([[confirmation bias]]). Reasoning is most effective when done as a collective—as demonstrated by the success of projects like [[science]]. They suggest that there are pressures not just individual, but [[group selection]] at play. Any group that managed to find ways of reasoning effectively would reap benefits for all its members, increasing their [[fitness (biology)|fitness]]. This could also help explain why humans, according to Sperber, are not optimized to reason effectively alone. Sperber's & Mercier's argumentative theory of reasoning claims that reason may have more to do with winning arguments than searching for the truth.<ref>{{multiref2
|1={{Cite journal| doi = 10.1017/S0140525X10000968 |pmid = 21447233|url = https://repository.upenn.edu/goldstone/15/| volume = 34| issue = 2| pages = 57–74| last1 = Mercier| first1 = Hugo| last2 = Sperber| first2 = Dan| title = Why Do Humans Reason? Arguments for an Argumentative Theory| journal = Behavioral and Brain Sciences| year = 2011|s2cid = 5669039}}
|2={{Cite book| publisher = Harvard University Press| isbn = 978-0674368309| last1 = Mercier| first1 = Hugo| last2 = Sperber| first2 = Dan| title = The Enigma of Reason| location = Cambridge| year = 2017}}
}}</ref>

===Reason in political philosophy and ethics===
{{Main|Political Philosophy|Ethics|The Good}}
[[Aristotle]] famously described reason (with language) as a part of [[human nature]], because of which it is best for humans to live "politically" meaning in communities of about the size and type of a small [[city state]] ({{transliteration|grc|polis}} in Greek). For example:
{{quote|text=It is clear, then, that a human being is more of a political [{{transliteration|grc|politikon}} = of the {{transliteration|grc|polis}}] animal [{{transliteration|grc|zōion}}] than is any bee or than any of those animals that live in herds. For nature, as we say, makes nothing in vain, and humans are the only animals who possess reasoned speech [{{transliteration|grc|logos}}]. Voice, of course, serves to indicate what is painful and pleasant; that is why it is also found in other animals, because their nature has reached the point where they can perceive what is painful and pleasant and express these to each other. But speech [{{transliteration|grc|logos}}] serves to make plain what is advantageous and harmful and so also what is just and unjust. For it is a peculiarity of humans, in contrast to the other animals, to have perception of good and bad, just and unjust, and the like; and the community in these things makes a household or city [{{transliteration|grc|polis}}].... By nature, then, the drive for such a community exists in everyone, but the first to set one up is responsible for things of very great goodness. For as humans are the best of all animals when perfected, so they are the worst when divorced from law and right. The reason is that injustice is most difficult to deal with when furnished with weapons, and the weapons a human being has are meant by nature to go along with prudence and virtue, but it is only too possible to turn them to contrary uses. Consequently, if a human being lacks virtue, he is the most unholy and savage thing, and when it comes to sex and food, the worst. But justice is something political [to do with the {{transliteration|grc|polis}}], for right is the arrangement of the political community, and right is discrimination of what is just.<ref name=Politics>{{cite book|author=[[Aristotle]]|title=[[Politics (Aristotle)|Politics]]|translator-first=Peter|translator-last=Simpson}}</ref>{{rp|at=I.2, 1253a}} }}

If human nature is fixed in this way, we can define what type of community is always best for people. This argument has remained a central argument in all political, ethical, and moral thinking since then, and has become especially controversial since firstly [[Rousseau]]'s Second Discourse, and secondly, the [[Theory of Evolution]]. Already in Aristotle there was an awareness that the {{transliteration|grc|polis}} had not always existed and had to be invented or developed by humans themselves. The household came first, and the first villages and cities were just extensions of that, with the first cities being run as if they were still families with Kings acting like fathers.{{r|Politics|at=I.2, 1252b15}}
<blockquote>[[Friendship]] seems to prevail in man and woman according to [[nature]] [{{transliteration|grc|kata phusin}}]; for people are by nature [{{transliteration|grc|tēi phusei}}] pairing more than political [{{transliteration|grc|politikon}}], in as much as the household [{{transliteration|grc|oikos}}] is prior and more necessary than the {{transliteration|grc|polis}} and making children is more common [{{transliteration|grc|koinoteron}}] with the animals. In the other animals, community [{{transliteration|grc|koinōnia}}] goes no further than this, but people live together [{{transliteration|grc|sumoikousin}}] not only for the sake of making children, but also for the things for life; for from the start the functions [{{transliteration|grc|erga}}] are divided, and are different for man and woman. Thus they supply each other, putting their own into the common [{{transliteration|grc|eis to koinon}}]. It is for these reasons that both utility and pleasure seem to be found in this kind of friendship.{{r|NE|at=[https://standardebooks.org/ebooks/aristotle/nicomachean-ethics/f-h-peters/text/book-8#chapter-8-1-12 VIII.12]}}</blockquote>

[[Rousseau]] in his Second Discourse finally took the shocking step of claiming that this traditional account has things in reverse: with reason, language, and rationally organized communities all having developed over a long period of time merely as a result of the fact that some habits of cooperation were found to solve certain types of problems, and that once such cooperation became more important, it forced people to develop increasingly complex cooperation—often only to defend themselves from each other.

In other words, according to Rousseau, reason, language, and rational community did not arise because of any conscious decision or plan by humans or gods, nor because of any pre-existing human nature. As a result, he claimed, living together in rationally organized communities like modern humans is a development with many negative aspects compared to the original state of man as an ape. If anything is specifically human in this theory, it is the flexibility and adaptability of humans. This view of the animal origins of distinctive human characteristics later received support from [[Charles Darwin]]'s [[Theory of Evolution]].

The two competing theories concerning the origins of reason are relevant to political and ethical thought because, according to the Aristotelian theory, a best way of living together exists independently of historical circumstances. According to Rousseau, we should even doubt that reason, language, and politics are a good thing, as opposed to being simply the best option given the particular course of events that led to today. Rousseau's theory, that human nature is malleable rather than fixed, is often taken to imply (for example by [[Karl Marx]]) a wider range of possible ways of living together than traditionally known.

However, while Rousseau's initial impact encouraged bloody revolutions against traditional politics, including both the [[French Revolution]] and the [[Russian Revolution (1917)|Russian Revolution]], his own conclusions about the best forms of community seem to have been remarkably classical, in favor of city-states such as [[Geneva]], and [[Arcadia (utopia)|rural living]].

==See also==
{{Portal|Philosophy|Psychology}}
* {{annotated link|[[Argument]]}}
* {{annotated link|[[Argumentation theory]]}}
* {{annotated link|[[Common sense]]}}
* {{annotated link|[[Confirmation bias]]}}
* {{annotated link|[[Conformity]]}}
* {{annotated link|[[Critical thinking]]}}
* {{annotated link|[[Logic and rationality]]}}
* [[Outline of thought]] – Topic tree that identifies many types of thoughts/thinking, types of reasoning, aspects of thought, related fields, and more
* [[Outline of human intelligence]] – Topic tree presenting the traits, capacities, models, and research fields of human intelligence, and more
* {{annotated link|[[Transduction (psychology)]]}}

==References==
{{Reflist}}

==Further reading==
{{Wiktionary|reason}}
{{wikiquote}}
* {{PhilPapers|category|reasoning}}
* Beer, Francis A., "Words of Reason", ''Political Communication'' 11 (Summer, 1994): 185–201.
* {{citation |year=1991 |author=Gilovich, Thomas |author-link=Thomas Gilovich |title=How We Know What Isn't So: The Fallibility of Human Reason in Everyday Life |place=New York |publisher=The [[Free Press (publisher)|Free Press]] |isbn=978-0029117057 |url=https://archive.org/details/howweknowwhatisn00gilorich }}
* Sciortino, Luca, "History of Rationalities: Ways of Thinking from Vico to Hacking and Beyond", Palgrave McMillan, Cham 2023 https://doi.org/10.1007/978-3-031-24004-1.

{{Age of Enlightenment}}
{{Human intelligence topics}}
{{Logic}}
{{Philosophical logic}}
{{Virtues}}

{{Authority control}}

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