An inner process stands in need of outward criteria.

Logic must look after itself. In a certain sense, we cannot make mistakes in logic.

It seems to me that, in every culture, I come across a chapter headed 'Wisdom.' And then I know exactly what is going to follow: 'Vanity of vanities, all is vanity.'

Uttering a word is like striking a note on the keyboard of the imagination.

Philosophy is not a theory but an activity.

My attitude towards him is an attitude towards a soul. I am not of the opinion that he has a soul. . . .

Don't get involved in partial problems, but always take flight to where there is a free view over the whole single great problem, even if this view is still not a clear one.