Liberty sustains the same relation to mind that space does to matter.

The way to be happy is to make others so.

It seems to me that if there is some infinite being who wants us to think alike he would have made us alike.

Darwin has done more to change human thought than all the priests who have existed.

My heart was filled with gratitude, with thankfulness, and went out in love to all the heroes, the thinkers who gave their lives for the liberty of hand and brain... to all the wise, the good, the brave of every land, whose thoughts and deeds have given freedom to the sons of men. And then I vowed to grasp the torch that they had held, and hold it high, that light might conquer darkness still.

We can be as honest as we are ignorant. If we are, when asked what is beyond the horizon of the known, we must say that we do not know.

The object of all education should be to increase the usefulness of man - usefulness to himself and others.