I inherited a vile melancholy from my father, which has made me mad all my life, at least not sober.

Gratitude is a species of justice.

All violation of established practice implies in its own nature a rejection of the common opinion, a defiance of common censure, and an appeal from general laws to private judgment: he, therefore, who differs form others without apparent advantage, ought not to be angry if his arrogance is punished with ridicule; if those whose example he superciliously overlooks, point him out to derision, and hoot him back again into the common road.

Human experience, which is constantly contradicting theory, is the great test of truth. A system, built upon the discoveries of a great many minds, is always of more strength, than what is produced by the mere workings of any one mind, which, of itself, can do very little. There is not so poor a book in the world that would not be a prodigious effort were it wrought out entirely by a single mind, without the aid of prior investigators.

The great source of pleasure is variety.

The perfect day for quitting is not real. It will never come, so might as well start today

Mankind have a great aversion to intellectual labor; but even supposing knowledge to be easily attainable, more people would be content to be ignorant than would take even a little trouble to acquire it.