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'.

Learn what is true in order to do what is right.

What are the moral convictions most fondly held by barbarous and semi-barbarous people? They are the convictions that authority is the soundest basis of belief; that merit attaches to readiness to believe; that the doubting disposition is a bad one, and skepticism is a sin.

Mr. Darwin's hypothesis is not, so far as I am aware, inconsistent with any known biological fact; on the contrary, if admitted, the facts of Development, of Comparative Anatomy, of Geographical Distribution, and of Palaeontology, become connected together, and exhibit a meaning such as they never possessed before; and I, for one, am fully convinced that if not precisely true, that hypothesis is as near an approximation to the truth as, for example, the Copernican hypothesis was to the true theory of the planetary motions.

I have endeavoured to show that no absolute structural line of demarcation, wider than that between the animals which immediately succeed us in the scale, can be drawn between the animal world and ourselves; and I may add the expression of my belief that the attempt to draw a physical distinction is equally futile, and that even the highest faculties of feeling and of intellect begin to germinate in lower forms of life.

Mathematics may be compared to a mill of exquisite workmanship, which grinds your stuff to any degree of fineness.

The great thing in the world is not so much to seek happiness as to earn peace and self-respect.