Whenever a text-book is written of real educational worth, you may be quite certain that some reviewer will say that it will be difficult to teach from it. Of course it will be difficult to teach from it. It it were easy, the book ought to be burned.

There are no whole truths: all truths are half-truths. It is trying to treat them as whole truths that plays to the devil.

The motive of success is not enough.

The absolute pacifist is a bad citizen; times come when force must be used to uphold right, justice and ideals.

[In many circumstances,] the most important thing about a proposition is not that it be true, but that it be interesting.

Fundamental progress has to do with the reinterpretation of basic ideas.

But harmony is limitation. Thus rightness of limitation is essential for growth of reality. Unlimited possibility and abstract creativity can procure nothing.