The aim of living is life itself.

The world only goes forward because of those who oppose it.

Impotent hatred is the most horrible of all emotions; one should hate nobody whom one cannot destroy.

Should I not be proud, when for twenty years I have had to admit to myself that the great Newton and all the mathematicians and noble calculators along with him were involved in a decisive error with respect to the doctrine of color, and that I among millions was the only one who knew what was right in this great subject of nature?

Tolerance comes of age. I see no fault committed that I myself could not have committed at some time or other.

All our knowledge is symbolic.

There is no crime of which I do not deem myself capable.