Now, in the second place, it was held originally that light was a series of corpuscles that flew off from a heated surface; but Thomas Young, about the year 1804, demonstrated the present accepted theory of light. But it was fought for years. Only after a long time did the scientific world give up its prejudice in favor of the theory that was propounded by Newton. But to-day we go back to Young, and see that he demonstrated it beyond question. In the third place, take another fact. Between 1830 and 1845 Faraday worked out a theory of electrical and magnetic phenomena. It was proved to be correct. Maxwell, a famous chemist in London, looked over the matter, and persuaded himself that Faraday was right; but nobody paid much attention to either of them; until after a while the scientific world, through the work of its younger men, those least wedded to the old-time beliefs, conceded that it must be true. The Nebular Theory was proved and worked out by Kant more than a hundred and thirty years ago. In 1799 Laplace worked it out again; but it was a long time before it was accepted. And now we go back to Kant and Laplace for our demonstration. Darwin's "Origin of Species" was published in 1859. But it was attacked by scientists as well as theologians on every hand. Huxley even looked at it with a good deal of hesitancy before he accepted it. To-day, however, everybody goes back to the "Origin of Species," and finds the whole thing there, demonstration and all. Lyell published a book on the antiquity of man in 1863. It was twenty- five years before all the scientific men of the world were ready to give up the idea that man had been on the earth more than six or eight thousand years. So we find that it is not theologians only; it is scientists, too, that find it difficult to accept new ideas. I know scientific men among my personal friends who are simply incapable of being hospitable to an idea that would compel them to reconstruct a theory that they have already accepted. Why are not all educated men Unitarians? Why do not scientific men accept demonstrated truth when it is first demonstrated as truth? It puts them to too much trouble. It touches their pride. They do not like to feel that they have thrown away half their lives following an hypothesis that is not capable of being substantiated.