Reason

Reason is a mental faculty found in humans, that is able to generate conclusions from assumptions or premises. In other words, it is amongst other things the means by which rational beings propose (specific) reasons, or explanations of cause and effect. In contrast to reason as an abstract noun, a reason is a consideration which explains or justifies.^[1]

Reason is particularly associated with human nature, that which is most unique and definitive about being human. As a way of coming to conclusions, it is often contrasted not only with the ways in which non-human animals appear to make decisions, but also with decisions based upon authority, intuition, emotion, mysticism, superstition, and faith. Reason is thought by rationalists to be more reliable in discovering what is true or what is best. The precise way in which reason differs from emotion, faith, and tradition is controversial, because all three are considered to be both potentially rational, and potentially in conflict with reason.

Contents 1 Reasons, reasoning, and rationality 2 Logical Reasoning Problem 3 Etymology 4 Reason compared to logic, cause-and-effect thinking, and symbolic thinking 5 Reason, truth, and "first principles" 6 Reason, imagination, mimesis, and memory 7 Reason and emotion or passion 8 Reason in political philosophy and ethics 9 Reason and faith 10 See also 11 Footnotes 12 References 13 Further reading

Reasons, reasoning, and rationality

Reason involves conscious explanations.

Logical Reasoning Problem

Reasoning as a process takes proposed explanations for considering, contrasting, or fitting them together in order to determine which beliefs, actions or attitudes are the best. Theoretical reasoning considers theoretical explanations in order to determine what to believe or accept as true. Practical reasoning considers what attitudes to have when taking actions.

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

Etymology

The meaning of the word "reason" in senses such as "human reason" overlaps to a large extent with "rationality" and the adjective of "reason" in philosophical contexts is normally "rational", rather than "reasoned" or "reasonable". The concept of "reason" is closely related to the concepts of language and logic, as reflected in the multiple meanings of the Greek word logos, the root of logic, which translated into Latin became ratio and then in French raison, from which the English word "reason" was derived.

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

In modern times, there is an increasing tendency to use the terms "logic" and "reason" interchangeably in philosophical discussion, or to see logic as the most pure or the defining form of reason.

Reason and logic can be thought of as distinct, although logic is one important aspect of reason. Reason is a type of thought. The word "logic" involves the attempt to describe rules by which reason operates, so that orderly reasoning can be taught. 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.^[2] 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. When Aristotle referred to "the logical" (hē logikē), he was referring more broadly to rational thought.^[3]

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.^[4]

Another way to consider the confusion between logic and reason is that computers and animals sometimes perform actions which are apparently logical: from a complex set of data, conclusions are achieved which are "logical". Being a cause of something which humans find logical does not necessarily mean that computers or animals have reason, or even logic in the strict sense. Some animals are also clearly capable of a type of "associative thinking"—even to the extent of associating causes and effects.^[5] A dog once kicked, can learn how to recognize the warning signs and avoid being kicked in the future. Human reason is something much more specific, requiring not just the possibility of associating perceptions of smoke, for example, with memories of fire, but also 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.^[6]

Thomas Hobbes described the creation of "Markes, or Notes of remembrance" (Leviathan Ch.4) as "speech" (allowing by his definition that it is not necessarily a means of communication or speech in the normal sense; he was clearly using "speech" as an English version of logos in this description^[7]). In the context of a language, these marks or notes are called "Signes" by Hobbes.

Reason, truth, and "first principles"

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.

Both Aristotle and Plato, like many philosophers throughout history, wrote about this question, which can be explained as follows.

People use logic, deduction, and induction, to reach conclusions they think are true. Conclusions reached in this way are considered more certain than sense perceptions on their own.^{[nb 1]} On the other hand, if such reasoned conclusions are only built originally upon a foundation of sense perceptions, then, the argument being considered goes, 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.^{[nb 2]}

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. Empiricism (sometimes associated with Aristotle^{[nb 3]} 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. 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, 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. Whereas secular reason begins with observable reality and applies logic to it to derive conclusions, theological reason begins with a predetermined conclusion or unquestionable sacred text and verifies it by using logic to reinterpret or to reject observable reality.

In Greek, "first principles" are archē, "starting points",^{[nb 4]} and the faculty used to perceive them is sometimes referred to in Aristotle^{[nb 5]} and Plato^{[nb 6]} as nous which was close in meaning to "awareness" or "consciousness".^{[nb 7]}

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. In the vision of these thinkers, reason is divine or at least has divine attributes. Such an approach allowed religious philosophers such as Thomas Aquinas and Étienne Gilson to try to show that reason and revelation are compatible. According to Hegel, "...the only thought which Philosophy bring 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."^[8]

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. For Descartes, Spinoza and Leibniz, this was associated with mathematics. 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, imagination, mimesis, and memory

Reason and imagination rely on similar mental processes.^[9] Imagination is not only found in humans. But Aristotle, for example, stated that phantasia (imagination: that which can hold images or phantasmata) and phronein (a type of thinking which can judge and understand in some sense) also exist in some animals.^[10] 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. This is equivalent to the habitual thinking about cause and effect discussed by Hume, and mentioned above. But this is not yet reason, because human imagination is different.

The recent modern writings of Terrence Deacon and Merlin Donald fit into an older tradition which makes reason connected to language, and mimesis,^{[nb 8]} but more specifically the ability to create language as part of an internal modeling of reality specific to humankind. Other results are consciousness, and imagination or fantasy. In more recent times, important areas of research include the relationship between reason and language, especially in discussions of origin of language. Modern proponents of a priori reasoning, at least with regards to language, include Noam Chomsky and Steven Pinker, to whom Donald and Deacon can be usefully contrasted.

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. Starting with a modern author, Merlin Donald writes^[11]

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

What Donald refers to here can be compared to Plato's term, eikasia as explained for example in Jacob Klein's commentary on Plato's dialog concerning learning, the Meno, which contains a long digression on this subject.^[12] According to this, an important aspect of human thinking in the Ancient Greek philosophical terminology of Plato is eikasia. This is the ability to perceive whether a perception is an image of something else, related somehow but not the same, and which therefore allows us to perceive that a dream or memory or a reflection in a mirror is not reality as such. 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 which are discussed above as definitive of reason. 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). This thinking (dianoia) is "an activity which consists in making the vast and diffuse jungle of the visible world depend on a plurality of more 'precise' noēta".^[13]

In turn, both Merlin Donald and the Socratic authors emphasize the importance of mimesis, often translated as "imitation". Donald writes^[14]

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.

Mimēsis is a concept, now popular again in academic discussion, which was particularly prevalent in Plato's works, and within Aristotle, it is discussed mainly in the Poetics. In Michael Davis's account of the theory of man in this work.^[15]

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...

...Thus Davis is here using "poetic" in an unusual sense, questioning the contrast in Aristotle between action (praxis, the praktikē) and making (poēsis, the 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.

We can also note that Donald also shares with Plato and Aristotle (especially in On Memory and Recollection), an emphasis upon the peculiarity in humans of voluntary initiation of a search through one's mental world. The ancient Greek anamnēsis, normally translated as "recollection" was opposed to mneme or "memory". Memory, shared with some animals,^[16] 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^[17] "but nothing except man is able to recollect".^[18] Recollection is a deliberate effort to search for and recapture something which was once known. Klein writes that, to "become aware of our having forgotten something means to begin recollecting".^[19]

Donald calls the same thing "autocueing", which he explains as follows:^[20]

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 on this subject of modern times, 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".

Reason and emotion or passion

In western literature, reason is often opposed to emotions or feelings—desires, fears, hates, drives, or passions. Even in everyday speech, westerners tend to say for example that their passions made them behave contrary to reason, or that their reason kept the passions under control (often expressed in colloquial terms as the dilemma between following "the head" (reason) "or the heart" (emotions)) . Many writers, such as Nikos Kazantzakis, extol passion and disparage reason.

It has also become common, particularly since the writings of Freud, to describe reason as the servant of the passions—the means of sorting out our desires and then getting what we want, or perhaps even the slave of the passions—allowing us to pretend to reason to the object of our desire. Such feigned reason is called "rationalization".

Philosophers such as Plato, Rousseau, Hume, Kierkegaard, and Nietzsche have combined both views—making rational thinking not only a tool of desires, but also something privileged within the spectrum of desires, being itself desired, and not only because of its usefulness in satisfying other desires.

Modern psychology has much to say on the role of emotions in belief formation. Deeper philosophical questions about the relation between belief and reality are studied in the field of epistemology, which forms part of the philosophical basis of science, a branch of human activity that specifically aims to determine (certain types of) truth by methods that avoid dependence on the emotions of the researchers.

Reason in political philosophy and ethics

Near the beginning of political philosophy, 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). For example...

It is clear, then, that a human being is more of a political [politikon = of the polis] animal [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 [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 [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 [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 polis], for right is the arrangement of the political community, and right is discrimination of what is just. (Aristotle's Politics 1253a 1.2. Peter Simpson's translation, with Greek terms inserted in square brackets.)

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. 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 polis had not always existed and had needed 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.^[21]...

Friendship [philia] seems to prevail [in] man and woman according to nature [kata phusin]; for people are by nature [tēi phusei] pairing [sunduastikon] more than political [politikon = of the polis], inasmuch as the household [oikos] is prior [proteron = earlier] and more necessary than the polis and making children is more common [koinoteron] with the animals. In the other animals, community [koinōnia] goes no further than this, but people live together [sumoikousin] not only for the sake of making children, but also for the things for life; for from the start the functions [erga] are divided, and are different [for] man and woman. Thus they supply each other, putting their own into the common [eis to koinon]. It is for these [reasons] that both utility [chrēsimon] and pleasure [hēdu] seem to be found in this kind of friendship. (Nicomachean Ethics, VIII.12.1162a. Rough literal translation with Greek terms shown in square brackets.)

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 in order 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 which has many negative aspects compared to the original state of man as an ape. If there be anything 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, there is a best way of living together which 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 which lead 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, 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 and faith

Though theologies and religions 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. Defenders of traditions and faiths from claims that they are irrationalist for ignoring or even attempting to forbid reason and argument concerning some subjects, typically maintain that there is no real conflict with reason, because reason itself is not enough to explain such things as the origins of the universe, or right and wrong, and so reason can and should be complemented by other sources of knowledge. The counter claim to this is that such a defense does not logically explain why arguments from reason would be forbidden or ignored.

There are enormously wide differences between different faiths, or even schools within different faiths, concerning this matter.

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. Leo Strauss spoke of a "Greater West" which 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 great Muslim philosopher Al-Farabi. In order to consider to what extent Eastern philosophy might have partaken of these important tensions, it is perhaps best to consider whether dharma or tao may be equivalent to Nature (by which we mean physis in Greek). According to Strauss^[22] 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 archē (first principles of knowledge) brought about a peculiar tension between reasoning on the one hand, and tradition or faith on the other.

A Hindu approach to faith and reason is summarized by Swami Tripurari:

Faith fully understood amounts to conformity to truth, whereas rational thought is but an imperfect means of apprehending truth. Conforming to truth involves apprehending or understanding it theoretically, but theoretically understanding truth does not necessarily involve conforming to it.^[23]

See also

Footnotes

1. ↑ Example: Metaphysics 981b: 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. "...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."
2. ↑ Metaphysics 1009b 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. "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 says1 that either there is no truth or we cannot discover it."
3. ↑ 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".
4. ↑ For example Aristotle Metaphysics 983a: ἐπεὶ δὲ φανερὸν ὅτι τῶν ἐξ ἀρχῆς αἰτίων δεῖ λαβεῖν ἐπιστήμην （τότε γὰρ εἰδέναι φαμὲν ἕκαστον, ὅταν τὴν πρώτην αἰτίαν οἰώμεθα γνωρίζειν） "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."
5. ↑ Example: Nicomachean Ethics 1139b: ἀμφοτέρων δὴ τῶν νοητικῶν μορίων ἀλήθεια τὸ ἔργον. καθ᾽ ἃς οὖν μάλιστα ἕξεις ἀληθεύσει ἑκάτερον, αὗται ἀρεταὶ ἀμφοῖν. The attainment of truth is then the function of both the intellectual parts of the soul. Therefore their respective virtues are those dispositions which will best qualify them to attain truth.
6. ↑ Example: Plat. Rep. 490b μιγεὶς τῷ ὄντι ὄντως, γεννήσας νοῦν καὶ ἀλήθειαν, γνοίη "consorting with reality really, he would beget intelligence and truth, attain to knowledge"
7. ↑ "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." "Progress or Return" in An Introduction to Political Philosophy: Ten Essays by Leo Strauss. (Expanded version of Political Philosophy: Six Essays by Leo Strauss, 1975.) Ed. Hilail Gilden. Detroit: Wayne State UP, 1989.
8. ↑ It should be noted that 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. See Mimesis.

References

Further reading

• Beer, Francis A., "Words of Reason", Political Communication 11 (Summer, 1994): 185-201.
• Gilovich, Thomas (1991), How We Know What Isn't So: The Fallibility of Human Reason in Everyday Life, New York: The Free Press, ISBN 0-02-911705-4 
• Tripurari, Swami, On Faith and Reason, The Harmonist, May 27, 2009.

Figures in the Age of Enlightenment by country or region   Notable figures America (English) Benjamin Franklin · Thomas Jefferson · James Madison · Thomas Paine America (Latin) Simón Bolívar  · Eugenio Espejo  · José Joaquín Fernández de Lizardi · Servando Teresa de Mier · Francisco de Miranda · Simón Rodríguez England Edward Gibbon · Thomas Hobbes  · Samuel Johnson · Edmund Burke (Irish born)  · John Locke  · Isaac Newton  · Robert Walpole France Montesquieu · François Quesnay · Voltaire · Buffon · Jean-Jacques Rousseau · Denis Diderot · Helvétius · Jean le Rond d'Alembert · Baron d'Holbach · Condorcet · Étienne Bonnot de Condillac Germany Immanuel Kant · Gotthold Ephraim Lessing · Johann Gottfried von Herder · Johann Wolfgang von Goethe · Friedrich Schiller · Moses Mendelssohn Greece Adamantios Korais · Rigas Feraios · Theophilos Kairis · Eugenios Voulgaris Hungary Ferenc Kazinczy · József Kármán · János Batsányi · Mihály Fazekas Italy Cesare Beccaria · Antonio Genovesi Low Countries Hugo Grotius · Baruch Spinoza · Franciscus van den Enden Poland-Lithuania Stanisław Konarski · Ignacy Krasicki · Hugo Kołłątaj · Stanisław Staszic · Jan Śniadecki · Julian Ursyn Niemcewicz · Jędrzej Śniadecki Portugal Sebastião José de Carvalho e Melo, Marquis of Pombal Russia Mikhail Lomonosov · Ivan Shuvalov · Ivan Betskoy · Ekaterina Dashkova · Nikolay Novikov · Mikhail Shcherbatov · Alexander Radishchev Scandinavia Anders Chydenius · Peter Forsskål · Gustav III · Ludvig Holberg · Arvid Horn · Johan Henric Kellgren · Eggert Ólafsson  · Henrik Gabriel Porthan · Jens Schielderup Sneedorff · Johann Friedrich Struensee · Emanuel Swedenborg Scotland Joseph Black · James Boswell · Robert Burns · Adam Ferguson · Francis Hutcheson · David Hume · James Hutton · Lord Kames · Lord Monboddo · James Macpherson · Thomas Reid · William Robertson · Adam Smith · Dugald Stewart · James Watt Serbia Dositej Obradović Spain Gaspar Melchor de Jovellanos · Benito Jerónimo Feijoo · Antonio de Ulloa Ukraine Hryhorii Skovoroda · Ivan Kotlyarevsky   Related topics Atheism · Capitalism · Civil liberties · Counter-Enlightenment · Critical thinking · Deism · Democracy · Empiricism · Enlightened absolutism · Free markets · Haskalah · Humanism · Liberalism · Natural philosophy · Rationality · Reason · Sapere aude · Science · Socialism · Secularism · French Encyclopédistes · Weimar Classicism

Logic   Related articles Academic areas Argumentation theory · Axiology · Critical thinking · Computability theory · Formal semantics · History of logic · Informal logic · Logic in computer science · Mathematical logic · Mathematics · Metalogic · Metamathematics · Model theory · Philosophical logic · Philosophy · Philosophy of logic · Philosophy of mathematics · Proof theory · Set theory Foundational concepts Abduction · Analytic truth · Antinomy · A priori · Deduction · Definition · Description · Entailment · Induction · Inference · Logical consequence · Logical form · Logical implication · Logical truth · Name · Necessity · Meaning · Paradox · Possible world · Presupposition · Probability · Reason · Reasoning · Reference · Semantics · Statement · Substitution · Syntax · Truth · Truth value · Validity   Philosophical logic Critical thinking and Informal logic Analysis · Ambiguity · Belief · Credibility · Evidence · Explanation · Explanatory power · Fact · Fallacy · Inquiry · Opinion · Parsimony · Premise · Propaganda · Prudence · Reasoning · Relevance · Rhetoric · Rigor · Vagueness Theories of deduction Constructivism · Dialetheism · Fictionalism · Finitism · Formalism · Intuitionism · Logical atomism · Logicism · Nominalism · Platonic realism · Pragmatism · Realism   Metalogic and Metamathematics Cantor's theorem · Church's theorem · Church's thesis · Consistency · Effective method · Foundations of mathematics · Gödel's completeness theorem · Gödel's incompleteness theorems · Soundness · Completeness · Decidability · Interpretation · Löwenheim–Skolem theorem · Metatheorem · Satisfiability · Independence · Type–token distinction · Use–mention distinction ·   Mathematical logic General Formal language · Formation rule · Formal system · Deductive system · Formal proof · Formal semantics · Well-formed formula · Set · Element · Class · Classical logic · Axiom · Natural deduction · Rule of inference · Relation · Theorem · Logical consequence · Axiomatic system · Type theory · Symbol · Syntax · Theory Traditional logic Proposition · Inference · Argument · Validity · Cogency · Syllogism · Square of opposition · Venn diagram Propositional calculus and Boolean logic Boolean functions · Propositional calculus · Propositional formula · Logical connectives · Quantifiers · Truth tables Predicate First-order · Quantifiers · Predicate · Second-order · Monadic predicate calculus Set theory Set · Empty set · Enumeration · Extensionality · Finite set · Function · Subset · Power set · Countable set · Recursive set · Domain · Range · Ordered pair · Uncountable set Model theory Model · Interpretation · Non-standard model · Truth value · Validity Proof theory Formal proof · Deductive system · Formal system · Theorem · Logical consequence · Rule of inference · Syntax Computability theory Recursion · Recursive set · Recursively enumerable set · Decision problem · Church–Turing thesis · Computable function · Primitive recursive function ·   Non-classical logic Modal logic Alethic · Axiologic · Deontic · Doxastic · Epistemic · Temporal Intuitionism Intuitionistic logic · Constructive analysis · Heyting arithmetic · Intuitionistic type theory · Constructive set theory · Fuzzy logic Degree of truth · Fuzzy rule · Fuzzy set · Fuzzy finite element · Fuzzy set operations · Substructural logic Structural rule · Relevance logic · Linear logic Paraconsistent logic Dialetheism Description logic Ontology  · Ontology language   Logicians Anderson · Aristotle · Averroes · Avicenna · Barwise · Bernays · Boole · Boolos · Cantor · Carnap · Church · Chrysippus · Curry · De Morgan · Frege · Geach · Gentzen · Gödel · Hilbert · Kleene · Kripke · Leibniz · Löwenheim · Peano · Peirce · Putnam · Quine · Russell · Scotus · Skolem · Smullyan · Tarski · Turing · Whitehead · William of Ockham · Wittgenstein · Zermelo   Lists Topics Outline of logic · Index of logic articles · Mathematical logic · Boolean algebra · Set theory Other Logicians · Rules of inference · Paradoxes · Fallacies · Logic symbols Portal · Category · Outline · WikiProject · Talk · changes