A theory of motivation is defective if it renders intelligible behaviour which is not intelligible.

equally real at all stages of his life; specifically, the fact that a particular stage is present cannot be regarded as conferring on it any special status.

To look for a single general theory of how to decide the right thing to do is like looking for a single theory of how to decide what to believe.

A person may be greedy, envious, cowardly, cold, ungenerous, unkind, vain, or conceited, but behave perfectly by a monumental act of the will.