I have found among my papers a sheet . . . in which I call architecture frozen music.

When ideas fail, words come in very handy.

What makes poetry? A full heart, brimful of one noble passion.

Oh how sweet it is to hear one's own convictions from another's lips.

Mathematics has the completely false reputation of yielding infallible conclusions. Its infallibility is nothing but identity. Two times two is not four, but it is just two times two, and that is what we call four for short. But four is nothing new at all. And thus it goes on and on in its conclusions, except that in the higher formulas the identity fades out of sight.

Where a man has a passion for meditating without the capacity of thinking, a particular idea fixes itself fast, and soon creates a mental disease.

Prudent and active men, who know their strength and use it with limit and circumspection, alone go far in the affairs of the world.