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This article is about the human faculty of reason and rationality. Reason_sentence_0

For other uses, see Reason (disambiguation). Reason_sentence_1

Reason is the capacity of consciously making sense of things, applying logic, and adapting or justifying practices, institutions, and beliefs based on new or existing information. Reason_sentence_2

It is closely associated with such characteristically human activities as philosophy, science, language, mathematics, and art, and is normally considered to be a distinguishing ability possessed by humans. Reason_sentence_3

Reason is sometimes referred to as rationality. Reason_sentence_4

Reasoning is associated with the acts of thinking and cognition, and involves using one's intellect. Reason_sentence_5

The field of logic studies the ways in which humans can use formal reasoning to produce logically valid arguments. Reason_sentence_6

Reasoning may be subdivided into forms of logical reasoning, such as: deductive reasoning, inductive reasoning, and abductive reasoning. Reason_sentence_7

Aristotle drew a distinction between logical discursive reasoning (reason proper), and intuitive reasoning, in which the reasoning process through intuition—however valid—may tend toward the personal and the subjectively opaque. Reason_sentence_8

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. Reason_sentence_9

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. Reason_sentence_10

Reasoning, like habit or intuition, is one of the ways by which thinking moves from one idea to a related idea. Reason_sentence_11

For example, reasoning is the means by which rational individuals understand sensory information from their environments, or conceptualize abstract dichotomies such as cause and effect, truth and falsehood, or ideas regarding notions of good or evil. Reason_sentence_12

Reasoning, as a part of executive decision making, is also closely identified with the ability to self-consciously change, in terms of goals, beliefs, attitudes, traditions, and institutions, and therefore with the capacity for freedom and self-determination. Reason_sentence_13

In contrast to the use of "reason" as an abstract noun, a reason is a consideration given which either explains or justifies events, phenomena, or behavior. Reason_sentence_14

Reasons justify decisions, reasons support explanations of natural phenomena; reasons can be given to explain the actions (conduct) of individuals. Reason_sentence_15

Using reason, or reasoning, can also be described more plainly as providing good, or the best, reasons. Reason_sentence_16

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." Reason_sentence_17

Psychologists and cognitive scientists have attempted to study and explain how people reason, e.g. which cognitive and neural processes are engaged, and how cultural factors affect the inferences that people draw. Reason_sentence_18

The field of automated reasoning studies how reasoning may or may not be modeled computationally. Reason_sentence_19

Animal psychology considers the question of whether animals other than humans can reason. Reason_sentence_20

Etymology and related words Reason_section_0

In the English language and other modern European languages, "reason", and related words, represent words which have always been used to translate Latin and classical Greek terms in the sense of their philosophical usage. Reason_sentence_21


  • The original Greek term was "λόγος" , the root of the modern English word "logic" but also a word which could mean for example "speech" or "explanation" or an "account" (of money handled).Reason_item_0_0
  • As a philosophical term logos was translated in its non-linguistic senses in Latin as . This was originally not just a translation used for philosophy, but was also commonly a translation for logos in the sense of an account of money.Reason_item_0_1
  • French is derived directly from Latin, and this is the direct source of the English word "reason".Reason_item_0_2

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 "logos", "ratio", "raison" and "reason" as interchangeable. Reason_sentence_22

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 "rational", rather than "reasoned" or "reasonable". Reason_sentence_23

Some philosophers, Thomas Hobbes for example, also used the word ratiocination as a synonym for "reasoning". Reason_sentence_24

Philosophical history Reason_section_1

The proposal that reason gives humanity a special position in nature has been argued to be a defining characteristic of western philosophy and later western modern science, starting with classical Greece. Reason_sentence_25

Philosophy can be described as a way of life based upon reason, and in the other direction reason has been one of the major subjects of philosophical discussion since ancient times. Reason_sentence_26

Reason is often said to be reflexive, or "self-correcting", and the critique of reason has been a persistent theme in philosophy. Reason_sentence_27

It has been defined in different ways, at different times, by different thinkers about human nature. Reason_sentence_28

Classical philosophy Reason_section_2

For many classical philosophers, nature was understood teleologically, meaning that every type of thing had a definitive purpose that fit within a natural order that was itself understood to have aims. Reason_sentence_29

Perhaps starting with Pythagoras or Heraclitus, the cosmos is even said to have reason. Reason_sentence_30

Reason, by this account, is not just one characteristic that humans happen to have, and that influences happiness amongst other characteristics. Reason_sentence_31

Reason was considered of higher stature than other characteristics of human nature, such as sociability, because it is something humans share with nature itself, linking an apparently immortal part of the human mind with the divine order of the cosmos itself. Reason_sentence_32

Within the human mind or soul (psyche), reason was described by Plato as being the natural monarch which should rule over the other parts, such as spiritedness (thumos) and the passions. Reason_sentence_33

Aristotle, Plato's student, defined human beings as rational animals, emphasizing reason as a characteristic of human nature. Reason_sentence_34

He defined the highest human happiness or well being (eudaimonia) as a life which is lived consistently, excellently and completely in accordance with reason. Reason_sentence_35

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. Reason_sentence_36

But teleological accounts such as Aristotle's were highly influential for those who attempt to explain reason in a way which is consistent with monotheism and the immortality and divinity of the human soul. Reason_sentence_37

For example, in the neo-platonist account of Plotinus, the cosmos has one soul, which is the seat of all reason, and the souls of all individual humans are part of this soul. Reason_sentence_38

Reason is for Plotinus both the provider of form to material things, and the light which brings individuals souls back into line with their source. Reason_sentence_39

Such neo-Platonist accounts of the rational part of the human soul were standard amongst medieval Islamic philosophers, and under this influence, mainly via Averroes, came to be debated seriously in Europe until well into the renaissance, and they remain important in Iranian philosophy. Reason_sentence_40

Subject-centred reason in early modern philosophy Reason_section_3

The early modern era was marked by a number of significant changes in the understanding of reason, starting in Europe. Reason_sentence_41

One of the most important of these changes involved a change in the metaphysical understanding of human beings. Reason_sentence_42

Scientists and philosophers began to question the teleological understanding of the world. Reason_sentence_43

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 "laws of nature" which affect inanimate things. Reason_sentence_44

This new understanding eventually displaced the previous world view that derived from a spiritual understanding of the universe. Reason_sentence_45

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. Reason_sentence_46

Any grounds of knowledge outside that understanding was, therefore, subject to doubt. Reason_sentence_47

In his search for a foundation of all possible knowledge, Descartes deliberately decided to throw into doubt all knowledge – except that of the mind itself in the process of thinking: Reason_sentence_48

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. Reason_sentence_49

Breaking with tradition and many thinkers after him, Descartes explicitly did not divide the incorporeal soul into parts, such as reason and intellect, describing them as one indivisible incorporeal entity. Reason_sentence_50

A contemporary of Descartes, Thomas Hobbes described reason as a broader version of "addition and subtraction" which is not limited to numbers. Reason_sentence_51

This understanding of reason is sometimes termed "calculative" reason. Reason_sentence_52

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. Reason_sentence_53

In the late 17th century, through the 18th century, John Locke and David Hume developed Descartes' line of thought still further. Reason_sentence_54

Hume took it in an especially skeptical direction, proposing that there could be no possibility of deducing relationships of cause and effect, and therefore no knowledge is based on reasoning alone, even if it seems otherwise. Reason_sentence_55

Hume famously remarked that, "We speak not strictly and philosophically when we talk of the combat of passion and of reason. Reason_sentence_56

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." Reason_sentence_57

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, 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." Reason_sentence_58

It followed from this that animals have reason, only much less complex than human reason. Reason_sentence_59

In the 18th century, Immanuel Kant attempted to show that Hume was wrong by demonstrating that a "transcendental" self, or "I", was a necessary condition of all experience. Reason_sentence_60

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. Reason_sentence_61

And so long as these limits are respected, reason can be the vehicle of morality, justice, aesthetics, theories of knowledge (epistemology), and understanding. Reason_sentence_62

Substantive and formal reason Reason_section_4

In the formulation of Kant, who wrote some of the most influential modern treatises on the subject, the great achievement of reason (German: Vernunft) is that it is able to exercise a kind of universal law-making. Reason_sentence_63

Kant was able therefore to reformulate the basis of moral-practical, theoretical and aesthetic reasoning, on "universal" laws. Reason_sentence_64

Here practical reasoning is the self-legislating or self-governing formulation of universal norms, and theoretical reasoning the way humans posit universal laws of nature. Reason_sentence_65

Under practical reason, the moral autonomy or freedom of human beings depends on their ability to behave according to laws that are given to them by the proper exercise of that reason. Reason_sentence_66

This contrasted with earlier forms of morality, which depended on religious understanding and interpretation, or nature for their substance. Reason_sentence_67

According to Kant, in a free society each individual must be able to pursue their goals however they see fit, so long as their actions conform to principles given by reason. Reason_sentence_68

He formulated such a principle, called the "categorical imperative", which would justify an action only if it could be universalized: Reason_sentence_69

In contrast to Hume then, Kant insists that reason itself (German ) has natural ends itself, the solution to the metaphysical problems, especially the discovery of the foundations of morality. Reason_sentence_70

Kant claimed that this problem could be solved with his "transcendental logic" which unlike normal logic is not just an instrument, which can be used indifferently, as it was for Aristotle, but a theoretical science in its own right and the basis of all the others. Reason_sentence_71

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?" Reason_sentence_72

Instead, the unity of reason has to be strictly formal, or "procedural". Reason_sentence_73

He thus described reason as a group of three autonomous spheres (on the model of Kant's three critiques): Reason_sentence_74


  1. Cognitive–instrumental reason is the kind of reason employed by the sciences. It is used to observe events, to predict and control outcomes, and to intervene in the world on the basis of its hypotheses;Reason_item_1_3
  2. Moral–practical reason is what we use to deliberate and discuss issues in the moral and political realm, according to universalizable procedures (similar to Kant's categorical imperative); andReason_item_1_4
  3. Aesthetic reason is typically found in works of art and literature, and encompasses the novel ways of seeing the world and interpreting things that those practices embody.Reason_item_1_5

For Habermas, these three spheres are the domain of experts, and therefore need to be mediated with the "lifeworld" by philosophers. Reason_sentence_75

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. Reason_sentence_76

The critique of reason Reason_section_5

Hamann, Herder, Kant, Hegel, Kierkegaard, Nietzsche, Heidegger, Foucault, Rorty, and many other philosophers have contributed to a debate about what reason means, or ought to mean. Reason_sentence_77

Some, like Kierkegaard, Nietzsche, and Rorty, are skeptical about subject-centred, universal, or instrumental reason, and even skeptical toward reason as a whole. Reason_sentence_78

Others, including Hegel, believe that it has obscured the importance of intersubjectivity, or "spirit" in human life, and attempt to reconstruct a model of what reason should be. Reason_sentence_79

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. Reason_sentence_80

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: Reason_sentence_81

For example, in opposition to subject-centred reason, Habermas has proposed a model of communicative reason that sees it as an essentially cooperative activity, based on the fact of linguistic intersubjectivity. Reason_sentence_82

Nikolas Kompridis has 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. Reason_sentence_83

The philosopher Charles Taylor, influenced by the 20th century German philosopher Martin Heidegger, has proposed that reason ought to include the faculty of disclosure, which is tied to the way we make sense of things in everyday life, as a new "department" of reason. Reason_sentence_84

In the essay "What is Enlightenment? Reason_sentence_85

", Michel Foucault proposed a concept of critique based on Kant's distinction between "private" and "public" uses of reason. Reason_sentence_86

This distinction, as suggested, has two dimensions: Reason_sentence_87


  • Private reason is 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".Reason_item_2_6
  • Public reason is 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_item_2_7

Reason compared to related concepts Reason_section_6

Compared to logic Reason_section_7

Main article: Logic Reason_sentence_88

The terms "logic" or "logical" are sometimes used as if they were identical with the term "reason" or with the concept of being "rational", or sometimes logic is seen as the most pure or the defining form of reason. Reason_sentence_89

For example in modern economics, rational choice is assumed to equate to logically consistent choice. Reason_sentence_90

Reason and logic can however be thought of as distinct, although logic is one important aspect of reason. Reason_sentence_91

Author Douglas Hofstadter, in Gödel, Escher, Bach, characterizes the distinction in this way. Reason_sentence_92

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. Reason_sentence_93

Reason is a type of thought, and the word "logic" involves the attempt to describe rules or norms by which reasoning operates, so that orderly reasoning can be taught. Reason_sentence_94

The oldest surviving writing to explicitly consider the rules by which reason operates are the works of the Greek philosopher Aristotle, especially Prior Analysis and Posterior Analysis. Reason_sentence_95

Although the Ancient Greeks had no separate word for logic as distinct from language and reason, Aristotle's newly coined word "syllogism" (syllogismos) identified logic clearly for the first time as a distinct field of study. Reason_sentence_96

When Aristotle referred to "the logical" (hē logikē), he was referring more broadly to rational thought. Reason_sentence_97

Reason compared to cause-and-effect thinking, and symbolic thinking Reason_section_8

Main articles: Causality and Symbols Reason_sentence_98

As pointed out by philosophers such as Hobbes, Locke and Hume, some animals are also clearly capable of a type of "associative thinking", even to the extent of associating causes and effects. Reason_sentence_99

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. Reason_sentence_100

It also does not mean that humans acting on the basis of experience or habit are using their reason. Reason_sentence_101

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. Reason_sentence_102

For reason to be involved, the association of smoke and the fire would have to be thought through in a way which can be explained, for example as cause and effect. Reason_sentence_103

In the explanation of Locke, for example, reason requires the mental use of a third idea in order to make this comparison by use of syllogism. Reason_sentence_104

More generally, reason in the strict sense requires the ability to create and manipulate a system of symbols, as well as indices and icons, according to Charles Sanders Peirce, the symbols having only a nominal, though habitual, connection to either smoke or fire. Reason_sentence_105

One example of such a system of artificial symbols and signs is language. Reason_sentence_106

The connection of reason to symbolic thinking has been expressed in different ways by philosophers. Reason_sentence_107

Thomas Hobbes described the creation of "Markes, or Notes of remembrance" (Leviathan Ch. Reason_sentence_108

4) as speech. Reason_sentence_109

He used the word speech as an English version of the Greek word logos so that speech did not need to be communicated. Reason_sentence_110

When communicated, such speech becomes language, and the marks or notes or remembrance are called "Signes" by Hobbes. Reason_sentence_111

Going further back, although Aristotle is a source of the idea that only humans have reason (logos), he does mention that animals with imagination, for whom sense perceptions can persist, come closest to having something like reasoning and nous, and even uses the word "logos" in one place to describe the distinctions which animals can perceive in such cases. Reason_sentence_112

Reason, imagination, mimesis, and memory Reason_section_9

Main articles: Imagination, Mimesis, Memory, and Recollection Reason_sentence_113

Reason and imagination rely on similar mental processes. Reason_sentence_114

Imagination is not only found in humans. Reason_sentence_115

Aristotle, for example, stated that phantasia (imagination: that which can hold images or phantasmata) and phronein (a type of thinking that can judge and understand in some sense) also exist in some animals. Reason_sentence_116

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 logos. Reason_sentence_117

But this is not yet reason, because human imagination is different. Reason_sentence_118

The recent modern writings of Terrence Deacon and Merlin Donald, writing about the origin of language, also connect reason connected to not only language, but also mimesis. Reason_sentence_119

More specifically they describe the ability to create language as part of an internal modeling of reality specific to humankind. Reason_sentence_120

Other results are consciousness, and imagination or fantasy. Reason_sentence_121

In contrast, modern proponents of a genetic predisposition to language itself include Noam Chomsky and Steven Pinker, to whom Donald and Deacon can be contrasted. Reason_sentence_122

As 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. Reason_sentence_123

Starting with a modern author, Merlin Donald writes Reason_sentence_124

In classical descriptions, an equivalent description of this mental faculty is eikasia, in the philosophy of Plato. Reason_sentence_125

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. Reason_sentence_126

What Klein refers to as dianoetic eikasia is the eikasia concerned specifically with thinking and mental images, such as those mental symbols, icons, signes, and marks discussed above as definitive of reason. Reason_sentence_127

Explaining reason from this direction: human thinking is special in the way that we often understand visible things as if they were themselves images of our intelligible "objects of thought" as "foundations" (hypothēses in Ancient Greek). Reason_sentence_128

This thinking (dianoia) is " activity which consists in making the vast and diffuse jungle of the visible world depend on a plurality of more 'precise' noēta". Reason_sentence_129

Both Merlin Donald and the Socratic authors such as Plato and Aristotle emphasize the importance of mimesis, often translated as imitation or representation. Reason_sentence_130

Donald writes Reason_sentence_131

Mimēsis is a concept, now popular again in academic discussion, that was particularly prevalent in Plato's works, and within Aristotle, it is discussed mainly in the Poetics. Reason_sentence_132

In Michael Davis's account of the theory of man in this work. Reason_sentence_133

Donald like Plato (and Aristotle, especially in On Memory and Recollection), emphasizes the peculiarity in humans of voluntary initiation of a search through one's mental world. Reason_sentence_134

The ancient Greek anamnēsis, normally translated as "recollection" was opposed to mneme or memory. Reason_sentence_135

Memory, shared with some animals, 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 eikasia "...but nothing except man is able to recollect." Reason_sentence_136

Recollection is a deliberate effort to search for and recapture something once known. Reason_sentence_137

Klein writes that, "To become aware of our having forgotten something means to begin recollecting." Reason_sentence_138

Donald calls the same thing autocueing, which he explains as follows: "Mimetic acts are reproducible on the basis of internal, self-generated cues. Reason_sentence_139

This permits voluntary recall of mimetic representations, without the aid of external cues – probably the earliest form of representational thinking." Reason_sentence_140

In a celebrated paper in modern times, the fantasy author and philologist J.R.R. Reason_sentence_141 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". Reason_sentence_142

Logical reasoning methods and argumentation Reason_section_10

A subdivision of philosophy is logic. Reason_sentence_143

Logic is the study of reasoning. Reason_sentence_144

Looking at logical categorizations of different types of reasoning, the traditional main division made in philosophy is between deductive reasoning and inductive reasoning. Reason_sentence_145

Formal logic has been described as the science of deduction. Reason_sentence_146

The study of inductive reasoning is generally carried out within the field known as informal logic or critical thinking. Reason_sentence_147

Deductive reasoning Reason_section_11

Main article: Deductive reasoning Reason_sentence_148

Deduction is a form of reasoning in which a conclusion follows necessarily from the stated premises. Reason_sentence_149

A deduction is also the conclusion reached by a deductive reasoning process. Reason_sentence_150

One classic example of deductive reasoning is that found in syllogisms like the following: Reason_sentence_151


  • Premise 1: All humans are mortal.Reason_item_3_8
  • Premise 2: Socrates is a human.Reason_item_3_9
  • Conclusion: Socrates is mortal.Reason_item_3_10

The reasoning in this argument is deductively valid because there is no way in which the premises, 1 and 2, could be true and the conclusion, 3, be false. Reason_sentence_152

Inductive reasoning Reason_section_12

Main article: Inductive reasoning Reason_sentence_153

Induction is a form of inference producing propositions about unobserved objects or types, either specifically or generally, based on previous observation. Reason_sentence_154

It is used to ascribe properties or relations to objects or types based on previous observations or experiences, or to formulate general statements or laws based on limited observations of recurring phenomenal patterns. Reason_sentence_155

Inductive reasoning contrasts strongly with deductive reasoning in that, even in the best, or strongest, cases of inductive reasoning, the truth of the premises does not guarantee the truth of the conclusion. Reason_sentence_156

Instead, the conclusion of an inductive argument follows with some degree of probability. Reason_sentence_157

Relatedly, the conclusion of an inductive argument contains more information than is already contained in the premises. Reason_sentence_158

Thus, this method of reasoning is ampliative. Reason_sentence_159

A classic example of inductive reasoning comes from the empiricist David Hume: Reason_sentence_160


  • Premise: The sun has risen in the east every morning up until now.Reason_item_4_11
  • Conclusion: The sun will also rise in the east tomorrow.Reason_item_4_12

Analogical reasoning Reason_section_13

Main article: Analogical reasoning Reason_sentence_161

Analogical reasoning is a form of inductive reasoning from a particular to a particular. Reason_sentence_162

It is often used in case-based reasoning, especially legal reasoning. Reason_sentence_163

An example follows: Reason_sentence_164


  • Premise 1: Socrates is human and mortal.Reason_item_5_13
  • Premise 2: Plato is human.Reason_item_5_14
  • Conclusion: Plato is mortal.Reason_item_5_15

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. Reason_sentence_165

Analogical reasoning often leads to wrong conclusions. Reason_sentence_166

For example: Reason_sentence_167


  • Premise 1: Socrates is human and male.Reason_item_6_16
  • Premise 2: Ada Lovelace is human.Reason_item_6_17
  • Conclusion: Therefore Ada Lovelace is male.Reason_item_6_18

Abductive reasoning Reason_section_14

Main article: Abductive reasoning Reason_sentence_168

Abductive reasoning, or argument to the best explanation, is a form of reasoning that doesn't fit in deductive or inductive, since it starts with incomplete set of observations and proceeds with likely possible explanations so the conclusion in an abductive argument does not follow with certainty from its premises and concerns something unobserved. Reason_sentence_169

What distinguishes abduction from the other forms of reasoning is an attempt to favour one conclusion above others, by subjective judgement or attempting to falsify alternative explanations or by demonstrating the likelihood of the favoured conclusion, given a set of more or less disputable assumptions. Reason_sentence_170

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. Reason_sentence_171

Fallacious reasoning Reason_section_15

Main articles: Fallacy, Formal fallacy, and Informal fallacy Reason_sentence_172

Flawed reasoning in arguments is known as fallacious reasoning. Reason_sentence_173

Bad reasoning within arguments can be because it commits either a formal fallacy or an informal fallacy. Reason_sentence_174

Formal fallacies occur when there is a problem with the form, or structure, of the argument. Reason_sentence_175

The word "formal" refers to this link to the form of the argument. Reason_sentence_176

An argument that contains a formal fallacy will always be invalid. Reason_sentence_177

An informal fallacy is an error in reasoning that occurs due to a problem with the content, rather than mere structure, of the argument. Reason_sentence_178

Traditional problems raised concerning reason Reason_section_16

Philosophy is sometimes described as a life of reason, with normal human reason pursued in a more consistent and dedicated way than usual. Reason_sentence_179

Two categories of problem concerning reason have long been discussed by philosophers concerning reason, essentially being reasonings about reasoning itself as a human aim, or philosophizing about philosophizing. Reason_sentence_180

The first question is concerning whether we can be confident that reason can achieve knowledge of truth better than other ways of trying to achieve such knowledge. Reason_sentence_181

The other question is whether a life of reason, a life that aims to be guided by reason, can be expected to achieve a happy life more so than other ways of life (whether such a life of reason results in knowledge or not). Reason_sentence_182

Reason versus truth, and "first principles" Reason_section_17

See also: Truth, First principle, and Nous Reason_sentence_183

Since classical times a question has remained constant in philosophical debate (which is sometimes seen as a conflict between movements called Platonism and Aristotelianism) concerning the role of reason in confirming truth. Reason_sentence_184

People use logic, deduction, and induction, to reach conclusions they think are true. Reason_sentence_185

Conclusions reached in this way are considered, according to Aristotle, more certain than sense perceptions on their own. Reason_sentence_186

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. Reason_sentence_187

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. Reason_sentence_188

In Greek, "first principles" are archai, "starting points", and the faculty used to perceive them is sometimes referred to in Aristotle and Plato as nous which was close in meaning to awareness or consciousness. Reason_sentence_189

Empiricism (sometimes associated with Aristotle but more correctly associated with 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. Reason_sentence_190

This approach always leads to the controversial conclusion that absolute knowledge is not attainable. Reason_sentence_191

Idealism, (associated with Plato and his school), claims that there is a "higher" reality, from which certain people can directly arrive at truth without needing to rely only upon the senses, and that this higher reality is therefore the primary source of truth. Reason_sentence_192

Philosophers such as Plato, Aristotle, Al-Farabi, Avicenna, Averroes, Maimonides, Aquinas and Hegel are sometimes said to have argued that reason must be fixed and discoverable—perhaps by dialectic, analysis, or study. Reason_sentence_193

In the vision of these thinkers, reason is divine or at least has divine attributes. Reason_sentence_194

Such an approach allowed religious philosophers such as Thomas Aquinas and Étienne Gilson to try to show that reason and revelation are compatible. Reason_sentence_195

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." Reason_sentence_196

Since the 17th century rationalists, reason has often been taken to be a subjective faculty, or rather the unaided ability (pure reason) to form concepts. Reason_sentence_197

For Descartes, Spinoza and Leibniz, this was associated with mathematics. Reason_sentence_198

Kant attempted to show that pure reason could form concepts (time and space) that are the conditions of experience. Reason_sentence_199

Kant made his argument in opposition to Hume, who denied that reason had any role to play in experience. Reason_sentence_200

Reason versus emotion or passion Reason_section_18

See also: Emotion and Passion (emotion) Reason_sentence_201

After Plato and Aristotle, western literature often treated reason as being the faculty that trained the passions and appetites. Reason_sentence_202

Stoic philosophy by contrast considered all passions undesirable. Reason_sentence_203

After the critiques of reason in the early Enlightenment the appetites were rarely discussed or conflated with the passions. Reason_sentence_204

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". Reason_sentence_205

Reason has been seen as a slave, or judge, of the passions, notably in the work of David Hume, and more recently of Freud. Reason_sentence_206

Reasoning which claims that the object of a desire is demanded by logic alone is called rationalization. Reason_sentence_207

Rousseau first proposed, in his second Discourse, that reason and political life is not natural and possibly harmful to mankind. Reason_sentence_208

He asked what really can be said about what is natural to mankind. Reason_sentence_209

What, other than reason and civil society, "best suits his constitution"? Reason_sentence_210

Rousseau saw "two principles prior to reason" in human nature. Reason_sentence_211

First we hold an intense interest in our own well-being. Reason_sentence_212

Secondly we object to the suffering or death of any sentient being, especially one like ourselves. Reason_sentence_213

These two passions lead us to desire more than we could achieve. Reason_sentence_214

We become dependent upon each other, and on relationships of authority and obedience. Reason_sentence_215

This effectively puts the human race into slavery. Reason_sentence_216

Rousseau says that he almost dares to assert that nature does not destine men to be healthy. Reason_sentence_217

According to Velkley, "Rousseau outlines certain programs of rational self-correction, most notably the political legislation of the Contrat Social and the moral education in Émile. Reason_sentence_218

All the same, Rousseau understands such corrections to be only ameliorations of an essentially unsatisfactory condition, that of socially and intellectually corrupted humanity." Reason_sentence_219

This quandary presented by Rousseau led to Kant's new way of justifying reason as freedom to create good and evil. Reason_sentence_220

These therefore are not to be blamed on nature or God. Reason_sentence_221

In various ways, German Idealism after Kant, and major later figures such Nietzsche, Bergson, Husserl, Scheler, and Heidegger, remain preoccupied with problems coming from the metaphysical demands or urges of reason. Reason_sentence_222

The influence of Rousseau and these later writers is also large upon art and politics. Reason_sentence_223

Many writers (such as Nikos Kazantzakis) extol passion and disparage reason. Reason_sentence_224

In politics modern nationalism comes from Rousseau's argument that rationalist cosmopolitanism brings man ever further from his natural state. Reason_sentence_225

Another view on reason and emotion was proposed in the 1994 book titled Descartes' Error by Antonio Damasio. Reason_sentence_226

In it, Damasio presents the "Somatic Marker Hypothesis" which states that emotions guide behavior and decision-making. Reason_sentence_227

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. Reason_sentence_228

Damasio further argues that rationality requires emotional input in order to function. Reason_sentence_229

Reason versus faith or tradition Reason_section_19

Main articles: Faith, Religion, and Tradition Reason_sentence_230

There are many religious traditions, some of which are explicitly fideist and others of which claim varying degrees of rationalism. Reason_sentence_231

Secular critics sometimes accuse all religious adherents of irrationality, since 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.). Reason_sentence_232

Though the theologies and religions such as classical monotheism typically do not claim to be 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. Reason_sentence_233

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: Reason_sentence_234


  • 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.Reason_item_7_19
  • 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"). For example, perhaps reason alone is not enough to explain such big questions as the origins of the universe, the origin of life, the origin of consciousness, the foundation of morality, or the destiny of the human race. 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.Reason_item_7_20
  • Tu quoque: Philosophers Alasdair MacIntyre and Charles Taylor argue that those critics of traditional religion who are adherents of secular liberalism are also sometimes guilty of ignoring, suppressing, and forbidding some kinds of reasoning about subjects. Similarly, philosophers of science such as Paul Feyarabend argue that scientists sometimes ignore or suppress evidence contrary to the dominant paradigm.Reason_item_7_21
  • 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 John 1: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".Reason_item_7_22

Some commentators have claimed that Western civilization can be almost defined by its serious testing of the limits of tension between "unaided" reason and faith in "revealed" truths—figuratively summarized as Athens and Jerusalem, respectively. Reason_sentence_235

Leo Strauss spoke of a "Greater West" that included all areas under the influence of the tension between Greek rationalism and Abrahamic revelation, including the Muslim lands. Reason_sentence_236

He was particularly influenced by the great Muslim philosopher Al-Farabi. Reason_sentence_237

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 (by which we mean physis in Greek). Reason_sentence_238

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. Reason_sentence_239

The philosophical concept of nature or natures as a way of understanding archai (first principles of knowledge) brought about a peculiar tension between reasoning on the one hand, and tradition or faith on the other. Reason_sentence_240

Although there is this special history of debate concerning reason and faith in the Islamic, Christian and Jewish traditions, the pursuit of reason is sometimes argued to be compatible with the other practice of other religions of a different nature, such as Hinduism, because they do not define their tenets in such an absolute way. Reason_sentence_241

Reason in particular fields of study Reason_section_20

Reason in political philosophy and ethics Reason_section_21

Main articles: Political Philosophy, Ethics, and The Good Reason_sentence_242

Aristotle famously described reason (with language) as a part of human nature, which means that it is best for humans to live "politically" meaning in communities of about the size and type of a small city state (polis in Greek). Reason_sentence_243

For example... Reason_sentence_244

The concept of human nature being fixed in this way, implied, in other words, that we can define what type of community is always best for people. Reason_sentence_245

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. Reason_sentence_246

Already in Aristotle there was an awareness that the polis had not always existed and had needed to be invented or developed by humans themselves. Reason_sentence_247

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. Reason_sentence_248

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. Reason_sentence_249

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. Reason_sentence_250

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. Reason_sentence_251

If anything is specifically human in this theory, it is the flexibility and adaptability of humans. Reason_sentence_252

This view of the animal origins of distinctive human characteristics later received support from Charles Darwin's Theory of Evolution. Reason_sentence_253

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. Reason_sentence_254

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 lead to today. Reason_sentence_255

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. Reason_sentence_256

However, while Rousseau's initial impact encouraged bloody revolutions against traditional politics, including both the French Revolution and the 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 rural living. Reason_sentence_257

Psychology Reason_section_22

Main article: Psychology of reasoning Reason_sentence_258

Scientific research into reasoning is carried out within the fields of psychology and cognitive science. Reason_sentence_259

Psychologists attempt to determine whether or not people are capable of rational thought in a number of different circumstances. Reason_sentence_260

Assessing how well someone engages in reasoning is the project of determining the extent to which the person is rational or acts rationally. Reason_sentence_261

It is a key research question in the psychology of reasoning. Reason_sentence_262

Rationality is often divided into its respective theoretical and practical counterparts. Reason_sentence_263

Behavioral experiments on human reasoning Reason_section_23

Experimental cognitive psychologists carry out research on reasoning behaviour. Reason_sentence_264

Such research may focus, for example, on how people perform on tests of reasoning such as intelligence or IQ tests, or on how well people's reasoning matches ideals set by logic (see, for example, the Wason test). Reason_sentence_265

Experiments examine how people make inferences from conditionals e.g., If A then B and how they make inferences about alternatives, e.g., A or else B. Reason_sentence_266

They test whether people can make valid deductions about spatial and temporal relations, e.g., A is to the left of B, or A happens after B, and about quantified assertions, e.g., All the A are B. Reason_sentence_267

Experiments investigate how people make inferences about factual situations, hypothetical possibilities, probabilities, and counterfactual situations. Reason_sentence_268

Developmental studies of children's reasoning Reason_section_24

Developmental psychologists investigate the development of reasoning from birth to adulthood. Reason_sentence_269

Piaget's theory of cognitive development was the first complete theory of reasoning development. Reason_sentence_270

Subsequently, several alternative theories were proposed, including the neo-Piagetian theories of cognitive development. Reason_sentence_271

Neuroscience of reasoning Reason_section_25

The biological functioning of the brain is studied by neurophysiologists and neuropsychologists. Reason_sentence_272

Research in this area includes research into the structure and function of normally functioning brains, and of damaged or otherwise unusual brains. Reason_sentence_273

In addition to carrying out research into reasoning, some psychologists, for example, clinical psychologists and psychotherapists work to alter people's reasoning habits when they are unhelpful. Reason_sentence_274

Computer science Reason_section_26

Automated reasoning Reason_section_27

Main articles: Automated reasoning and Computational logic Reason_sentence_275

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. Reason_sentence_276

Meta-reasoning Reason_section_28

Main article: Metacognition Reason_sentence_277

Meta-reasoning is reasoning about reasoning. Reason_sentence_278

In computer science, a system performs meta-reasoning when it is reasoning about its own operation. Reason_sentence_279

This requires a programming language capable of reflection, the ability to observe and modify its own structure and behaviour. Reason_sentence_280

Evolution of reason Reason_section_29

A species could benefit greatly from better abilities to reason about, predict and understand the world. Reason_sentence_281

French social and cognitive scientists Dan Sperber and Hugo Mercier argue that there could have been other forces driving the evolution of reason. Reason_sentence_282

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). Reason_sentence_283

Reasoning is most effective when it is done as a collective – as demonstrated by the success of projects like science. Reason_sentence_284

They suggest that there are not just individual, but group selection pressures at play. Reason_sentence_285

Any group that managed to find ways of reasoning effectively would reap benefits for all its members, increasing their fitness. Reason_sentence_286

This could also help explain why humans, according to Sperber, are not optimized to reason effectively alone. Reason_sentence_287

Their argumentative theory of reasoning claims that reason may have more to do with winning arguments than with the search for the truth. Reason_sentence_288

See also Reason_section_30


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