Every man should be responsible to others, nor should any one be allowed to do just as he pleases; for where absolute freedom is allowed, there is nothing to restrain the evil which is inherent in every man.

The mathematical sciences particularly exhibit order symmetry and limitations; and these are the greatest forms of the beautiful.

We do not know a truth without knowing its cause.

Metaphysics is universal and is exclusively concerned with primary substance. ... And here we will have the science to study that which is, both in its essence and in the properties which it has.

Education begins at the level of the learner.

By 'life,' we mean a thing that can nourish itself and grow and decay.

Anger is always concerned with individuals, ... whereas hatred is directed also against classes: we all hate any thief and any informer. Moreover, anger can be cured by time; but hatred cannot. The one aims at giving pain to its object, the other at doing him harm; the angry man wants his victim to feel; the hater does not mind whether they feel or not.