Reason denotes that function of our intelligence which has reference to the attainment of a particular class of truths. We know a great many things by immediate or actual experience. Our senses tell us that we are thirsty, that we hear a sound, that we are affected by light. These facts are truths of sense or of immediate knowedge, and do not involve the reason. Reason comes into play when we know a thing not immediately, but by some indirect process; as when, from seeing a river unusually swollen, we believe that there have been heavy rains at its sources. Here the mere sense tells us only that the river is high. It is by certain transitions of thought, or by the employment of our thinlking powers, that we come to know the other circumstance — that in a remote part of the country there have been heavy rains.
In ascertaining these truths of reason or of inference, as they are called. there are various steps or operations, described ulnder (different names. Thus we have (1) Deduction, or Syllogism; (2) Induction; and( (3) Generalization of notions, of which Abstraction and Definition are various phases. These are well represented by their several designations. The nature of the function or faculty denominated Reason, or the Reasoning Faculty, can be explained by showing how it results from the fundamental powers of the intelligence.
There is anoter anand peculiar simgniication attached to the word reason, growing out of the philosophy of Kant (q.v.), which maintains a distinction between reason and understanding, the latter being that faculty called by the Greeks νοῦς, and by Hamilton called the "Regulative Faculty." See Fleming and Krauth, Vocab. of Philosophy, s.v.