A high degree of intellect tends to make a man unsocial.

The fourfold root of the principle of sufficent reason is "Anything perceived has a cause. All conclusions have premises. All effects have causes. All actions have motives.

In our early youth we sit before the life that lies ahead of us like children sitting before the curtain in a theatre, in happy and tense anticipation of whatever is going to appear. Luckily we do not know what really will appear.

Patriotism, when it wants to make itself felt in the domain of learning, is a dirty fellow who should be thrown out of doors.

To attain something desired is to discover how vain it is; and…though we live all our lives in expectation of better things, we often at the same time long regretfully for what is past. The present, on the other hand, is regarded as something quite temporary and serving only as the road to our goal. That is why most men discover when they look back on their life that they have the whole time been living ad interim, and are surprised to see that which they let go by so unregarded and unenjoyed was precisely their life, was precisely in expectation of which they lived.

Genius and madness have something in common: both live in a world that is different from that which exists for everyone else.

Empirical sciences prosecuted purely for their own sake, and without philosophic tendency are like a face without eyes.