This has been my life. I have found it worth living, and would gladly live it again if the second chance were offered me.

We must be skeptical even of our skepticism.

When two men of science disagree, they do not invoke the secular arm; they wait for further evidence to decide the issue, because, as men of science, they know that neither is infallible. But when two theologians differ, since there is no criteria to which either can appeal, there is nothing for it but mutual hatred and an open or covert appeal to force.

Men are born ignorant, not stupid. They are made stupid by education.

Mathematics takes us into the region of absolute necessity, to which not only the actual word, but every possible word, must conform.

An educator should think of a child as a gardener thinks of a plant, as something to be made to grow by having the right soil and the right amount of water. If your roses fail to bloom, it does not occur to you to whip them, but you try to find out what has been amiss in your treatment of them. ... The important thing is what the children do, and not what they do not do. And what they do, if it is to have value, must be a spontaneous expression of their own vital energy.

So far I have been speaking of theoretical science, which is an attempt to understand the world. Practical science, which is an attempt to change the world, has been important from the first, and has continually increased in importance, until it has almost ousted theoretical science from men's thoughts.