Reason, in philosophy, is the ability to form and operate upon concepts in abstraction, in accordance with rationality and logic. Discussion and debate about the nature, limits, and causes of reason have been important through the history of philosophy. Discussion about reason especially concerns:
Reason, like consciousness, with which it is also intimately connected, has traditionally been claimed as a distinctly human capacity, not to be found elsewhere in the animal world. However, recent studies in animal cognition show that animals are capable of some types of on a lower level thinking similar to that of humans.
The English term “reason” is derived from the French word raison, from Latin rationem (ratio) "reckoning, understanding, motive, cause." The concept of reason is connected to the concept of language, as reflected in the meanings of the Greek word, "logos." As reason, rationality, and logic are all associated with the ability of the human mind to predict effects as based upon presumed causes, the word "reason" also denotes a ground or basis for a particular argument, and hence is used synonymously with the word "cause."
Reason is the means by which human beings achieve understanding by integrating perceptions received through the senses with concepts and associating them with knowledge already acquired. Reason is also the process of evaluating and manipulating ideas and facts.
The fundamental attribute of reason is clarity, and the use of identifiable ideas, memories, emotions, and sensory input. Since reason is a means of achieving understanding, its method is significant. Reason is organized, systematic, and a purposeful way of thinking. Reason also makes use of vehicles such as logic, deduction, and induction to make sense of perceptions and knowledge.
While reason is a type of thought, logic is a field of study which categorizes ways of justifying conclusions that are in accordance with reason. This distinction between reason and logic originates with the writings of Aristotle. Although the Greeks had no separate word for logic as opposed to language and reason, Aristotle's neologism "syllogism" (syllogismos) identified logic clearly for the first time as a distinct field of study. (When Aristotle referred to "the logical," the source of our word "logic," he was referring more broadly to reason or “the rational.”)
Although logic is an important aspect of reason, logic and reason are not synonymous. The modern tendency to prefer "hard logic," or "solid logic," has incorrectly led to the two terms occasionally being seen as essentially interchangeable, or to the conception that logic is the defining and pure form of reason.
Animals and machines (including computers) can unconsciously perform logical operations, and many animals (including humans) can unconsciously associate different perceptions as causes and effects and then make decisions and even plans. "Reason" is the type of thinking which combines language, consciousness, and logic, something that at this time, only humans are known to be able to do.
Although the relationship between reason and logic has been under discussion for a long time, the neurologist Terrence Deacon, following the tradition of Peirce, has recently offered a useful new description in modern terms. Like many philosophers in the English tradition of Hobbes, Locke, and Hume, he starts by distinguishing the type of thinking which is most essential to human rational thinking as a type of associative thinking. Reason by his account therefore requires associating perceptions in a way which may be arbitrary (or nominal, conventional, or "formal"). The image or "icon" of smoke may not only be related with the image of fire, but, for example, with the English word "smoke," or with any made-up symbol (not necessarily a spoken word). What is essentially rational, or at least essentially human, is however not the arbitrariness of symbols, but rather, how they are used.
"In theory, there is no difference between theory and practice. But, in practice, there is." —Jan L. A. van de Snepscheut
"Speculative reason" or "pure reason" is theoretical (or logical, deductive) thought (sometimes called theoretical reason), as opposed to practical (active, willing) thought. "Practical reason" is the application of reason in deciding on a course of action, while speculative (or theoretical) reason is concerned with absolute and universal truths. For example, deciding exactly how to build a telescope is practical reason, whereas deciding between two theories of light and optics is speculative reason.
The distinction between practical and speculative reason was made by the ancient Greek philosophers Plato and Aristotle, who distinguished between theory (theoria, or a wide or clear vision of its structure) and practice (praxis), as well as productive knowledge (techne).
Speculative reason is contemplative, detached, and certain, whereas practical reason is engaged, involved, active, and dependent upon the specifics of the situation. Speculative reason provides the universal, necessary principles of logic, such as the principle of contradiction, which must apply everywhere, regardless of the specifics of the situation. Practical reason, on the other hand, is that power of the mind engaged in deciding what to do. It is also referred to as moral reason, because it involves action, decision, and particulars. Though many other thinkers have erected systems based on the distinction, two important later thinkers who have done so are Aquinas (who follows Aristotle in many respects) and Kant.
In cognitive research, "practical reason" is the process of ignoring unproductive (or undesirable) possibilities in favor of productive possibilities. It is considered a form of cognitive bias, because it is illogical.
In ancient Greek philosophy a conflict arose between the Platonists and the Aristotelians over the role of reason in confirming truth. Both Aristotle and Plato recognized this as one of the essential questions of philosophy. Human beings use logical syllogisms such as deduction and inductive reasoning to reach conclusions which they feel are more infallible than basic sense perceptions. However, if such conclusions are built only upon sense perceptions, even the most logical conclusions can never be said to be certain, because they are built upon fallible perceptions (or fallible interpretations of perceptions). It is clear that human beings desire to know things with certainty, and that human beings are certain about some things. These things which are known with certainty are referred to as “first principles.”
What is the source of these first principles? Is the source only experience, as claimed in "empiricist" arguments (considered by some as being Aristotelian, and more recently associated with British philosophers such as David Hume)? Or is there some other “faculty” from which we derive our consciousness of at least some "a priori" truths (a position called “idealist” and associated with Platonism)? Or are there certain undeniable axioms that form the base for all other faculties and experiences (a position supported by the Scottish School of Common Sense as exemplified by Thomas Reid, and more recently by Objectivism)?
In view of all these considerations, we arrive at the idea of a special science which can be entitled the Critique of Pure Reason. For reason is the faculty which supplies the principles of a priori knowledge. Pure reason is, therefore, that which contains the principles whereby we know anything absolutely a priori. An organon of pure reason would be the sum-total of those principles according to which all modes of pure a priori knowledge can be acquired and actually brought into being. The exhaustive application of such an organon would give rise to a system of pure reason. But as this would be asking rather much, and as it is still doubtful whether, and in what cases, any extension of our knowledge be here possible, we can regard a science of the mere examination of pure reason, of its sources and limits, as the propaedeutic to the system of pure reason. (Immanuel Kant, sec VII. "The Idea and Division of a Special Science," Critique of Pure Reason)
In Greek philosophy, “first principles” were “arkhai,” starting points, and the faculty used to perceive them was sometimes referred to in Aristotle and Plato as “nous,” which was close in meaning to “awareness” and therefore “consciousness.” The question of whether we become aware of “arkhai” by building up and comparing experiences, or in some other way, was left unanswered.
Modern proponents of a priori reasoning, at least with regards to language, are Noam Chomsky and Steven Pinker, to whom Merlin Donald and Terrence Deacon can be contrasted.
The recent writings of Merlin Donald and Terrence Deacon fit into an older tradition which makes reason connected to language, and mimesis, 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.
Thomas Hobbes describes 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; in this description he was presumably thinking of "speech" as an English version of "logos"). In the context of a language, these marks or notes are called "Signes" by Hobbes.
In literature, reason is often placed in opposition to emotions, feelings, desires, drives or passions. Others make reason the servant or tool of emotion and desire, a means of comprehending desire and discovering how to fulfill it. Some philosophers including Plato, Rousseau, Hume, and Nietzsche combined both views, making rational thinking not only a servant of desire, but also something which is desired in itself.
The question of whether reason is in fact driven by emotions is important in philosophy, because reason is seen by almost all philosophers as the means by which we come to know the truth, and truth as something objective which exists outside of human consciousness. If reason is affected by emotions, how can we be certain that we are not deceiving ourselves by ignoring undesirable information, or by misinterpreting information in accordance with our unconscious desires?
Sometimes reason clearly seems to come into conflict with certain human desires. Human beings sometimes make choices on the basis of an association of ideas which is an artificially constructed model, rather than an association based on raw experience or passion. Examples are compliance with civil laws or social customs, or the acceptance of religious precepts and discipline.
In theology, reason, as distinguished from faith, is the human critical faculty exercised upon religious truth, whether by way of discovery or by way of explanation. Some commentators have claimed that Western civilization can be almost defined by the tension between “unaided” reason and faith in "revealed" truths, figuratively represented 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. Strauss was particularly influenced by the great Muslim philosopher Al-Farabi.
The limits within which reason may be used have been prescribed differently in different religious traditions and during different periods of thought. Modern religious thought tends to allow to reason a wide field, reserving as the domain of faith the ultimate (supernatural) truths of theology.
Wilhelm Reich, the controversial Austrian psychiatrist and naturalist, followed in Hegel's footsteps in perceiving reason not as a reduction to analytic deduction or mechanistic one-dimensional induction, but as being a primal part of the depth structure of nature itself; "a trait that pulsated from the heart of nature and was thus manifested in all living things." Viewed in these terms reason becomes an ontological term rather than an epistemological one. Reason is understood here as having an objective existence apart from its relation to the mental operations of any observer.
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