The acorn becomes an oak by means of automatic growth; no commitment is necessary. The kitten similarly becomes a cat on the basis of instinct. Nature and being are identical in creatures like them. But a man or woman becomes fully human only by his or her choices and his or her commitment to them. People attain worth and dignity by the multitude of decisions they make from day by day. These decisions require courage.

Ch. 1 : The Courage to Create, p. 21 - The Courage to Create (1975)