Time is relative; its only worth depends upon what we do as it is passing.

Considered logically this concept is not identical with the totality of sense impressions referred to; but it is an arbitrary creation of the human (or animal) mind.

All these primary impulses, not easily described in words, are the springs of man's actions.

We can invent as many theories we like, and any one of them can be made to fit the facts. But that theory is always preferred which makes the fewest number of assumptions.

Man can find meaning in life only through devoting himself to society.

The mind that opens to a new idea never returns to its original size

The most fundamental question we can ever ask ourselves is whether or not the universe we live in is friendly or hostile.