The only people, scientific or other, who never make mistakes are those who do nothing.

I am content with nothing, restless and ambitious... and I despise myself for the vanity, which formed half the stimulus to my exertions. Oh would that I were one of those plodding wise fools who having once set their hand to the plough go on nothing doubting.

The man who is all morality and intellect, although he may be good and even great, is, after all, only half a man.

Science reckons many prophets, but there is not even a promise of a Messiah.

Matter and force are the two names of the one artist who fashions the living as well as the lifeless.

Logical consequences are the scarecrows of fools and the beacons of wise men.

It is not what we believe, but why we believe it. Moral responsibility lies in diligently weighing the evidence. We must actively doubt; we have to scrutinize our views, not take them on trust. No virtue attached to blindly accepting orthodoxy, however 'venerable'.