Intelligence is the only moral guide.

Temptations are as thick as the leaves of the forest, and no one can be out of the reach of temptation unless he is dead. The great thing is to make people intelligent enough and strong enough, not to keep away from temptation, but to resist it.

All religion is slavery.

Too much doubt is better than too much credulity.

I am anxious to give away information, for it is only by giving it away that you can keep it. When you have told it, you remember it. It is with information as it is with liberty, the only way to be dead sure of it is to give it to other people.

If we should put god in the Constitution there would be no room left for man.

There is no harmony between religion and science. When science was a child, religion sought to strangle it in the cradle. Now that science has attained its youth, and superstition is in its dotage, the trembling, palsied wreck says to the athlete: "Let us be friends."