A theory is the more impressive the greater the simplicity of its premises is, the more different kinds of things it relates, and the more extended its area of applicability.
Pablo Casals is a very great artist. What I admire is the firm stand he has taken not only against the oppressors of his countrymen, but also against those opportunists who are always ready to compromise with the Devil. He perceives clearly that the world is in greater peril from those who tolerate or encourage evil than from those who actually commit it.
No matter how we may single out a complex from nature...its theoretical treatment will never prove to be ultimately conclusive... I believe that this process of deepening of theory has no limits.
The satisfaction of physical needs is indeed the indispensable pre-condition of a satisfactory existence, but in itself it is not enough. In order to be content, men must also have the possibility of developing their intellectual and artistic powers to whatever extent accords with their personal characteristics and abilities.