Sit down before fact as a little child, be prepared to give up every conceived notion, follow humbly wherever and whatever abysses nature leads, or you will learn nothing.

Living things have no inertia, and tend to no equilibrium.

I'd rather have an ape for an ancestor than a bishop.

The only medicine for suffering, crime, and all other woes of mankind, is wisdom. Teach a man to read and write, and you have put into his hands the great keys of the wisdom box. But it is quite another thing to open the box.

The dogma of the infallibility of the Bible is no more self-evident than is that of the infallibility of the popes.

My business is to teach my aspirations to confirm themselves to fact, not to try and make facts harmonize with my aspirations.

Creation,' in the ordinary sense of the word, is perfectly conceivable. I find no difficulty in conceiving that, at some former period, this universe was not in existence, and that it made its appearance in six days (or instantaneously, if that is preferred), in consequence of the volition of some preexisting Being.