1911 Encyclopædia Britannica/Reason
REASON (Lat. ratio, through French raison), in philosophy, the faculty or process of drawing logical inferences. Thus we speak of man as essentially a rational animal, it being implied that man differs from all other animals in that he can consciously draw inferences from premises. It is, however, exceedingly difficult in this respect to draw an absolute distinction between men and animals, observation of which undoubtedly suggests that the latter have a certain power of making inferences. Between the higher animals and the lower types of mankind the distinction is so hard to draw that many psychologists argue that the difference is one of degree rather than of kind (see also Instinct). There can be little doubt, however, that inference by man differs from that of the brute creation in respect of self-consciousness, and, though there can be no doubt that some animals dream, it is difficult to find evidence for the presence of ideal images in the minds of any but the highest animals. In the nature of the case satisfactory conclusions as to the rationality which may be predicated of animals are impossible.
The term "reason" is also used in several narrower senses. Thus reason is opposed to sensation, perception, feeling, desire, as the faculty (the existence of which is denied by empiricists) by which fundamental truths are intuitively apprehended. These fundamental truths are the causes or "reasons" (ἁρχαί) of all derivative facts. With Kant, reason (Vernunft) is the power of synthesizing into unity, by means of comprehensive principles, the concepts provided by the intellect (Verstand). The reason which gives a priori principles Kant calls "Pure Reason" (cf. the Kritik der reinen Vernunft), as distinguished from the "Practical Reason" (praktische Vernunft) which is specially concerned with the performance of particular actions. In formal logic the drawing of inferences (frequently called "ratiocination," from Lat. ratiocinari, to use the reasoning faculty) is classified from Aristotle downwards as deductive (from generals to particulars) and inductive (from particulars to generals); see Logic, Induction, Syllogism. In theology, reason, as distinguished from faith, is the human intelligence exercised upon religious truth whether by way of discovery or by way of explanation. The limits within which the reason may be used have been laid down differently in different churches and periods of thought: on the whole, modern Christianity, especially in the Protestant churches, tends to allow to reason a wide field, reserving, however, as the sphere of faith the ultimate (supernatural) truths of theology.
The Greek words for reason are νοῦς and λόγος, both vaguely used. In Aristotle the λόγος of a thing is its definition, including its formal cause, while the ultimate principles of a science are ἁρχαί, the "reasons" (in a common modern sense) which explain all its particular facts. Nois in Plato and Aristotle is used both widely for all the meanings which "reason" can have, and strictly for the faculty which apprehends intuitively. Thus, in the Republic, van is the faculty which apprehends necessary truth, while δόξα (opinion) is concerned with phenomena.
- The Schoolmen's distinction of ratio cognoscendi (a reason for acknowledging a fact) and ratio essendi (a reason for the existence of this fact).