Movement will fail sooner than usefulness.

The poet ranks far below the painter in the representation of visible things, and far below the musician in that of invisible things.

Anyone who invokes authors in discussion is not using his intelligence but his memory.

The limiting surface of one thing is the beginning of another.

He who does not understand the supreme certainty of mathematics is wallowing in confusion.

If you throw a stone in a pond... the waves which strike against the shores are thrown back towards the spot where the stone struck; and on meeting other waves they never intercept each other's course... In a small pond one and the same stroke gives birth to many motions of advance and recoil.

Especially learn how to see.