Common-sense knowledge is prompt, categorical, and inexact.

The power of understanding symbols, i.e. of regarding everything about a sense-datum as irrelevant except a certain form that it embodies, is the most characteristic mental trait of mankind. It issues in an unconscious, spontaneous process of abstraction, which goes on all the time in the human mind: a process of recognizing the concept in any configuration given to experience, and forming a conception accordingly. That is the real sense of Aristotle's definition of Man as "the rational animal".

To trace the development of mind from earliest times ... requires ... not a categorical concept, but a functional one.... The most promising operational principle for this purpose is the principle of individuation.

Art is the creation of forms symbolic of human feeling.

Music is our myth of the inner life.

A mind that is very selective to forms... is apt to use its images metaphorically, to exploit their possible significance for the conception of remote or intangible ideas.

Nature, as man has always known it, he knows no more. Since he has learned to esteem signs above symbols, to suppress his emotional reactions in favor of practical ones and make use of nature instead of holding so much of it sacred, he has altered the face, if not the heart, of reality.