It is, therefore, the quest of this special beauty, the sense of the harmony of the cosmos, which makes us choose the facts most fitting to contribute to this harmony, just as an artist chooses from among the features of his model those which perfect the picture and give it character and life. And we need not fear that this instinctive and unavowed prepossession will turn the scientist aside from the search for the true. One may dream a harmonious world, but how far the real world will leave it behind! The greatest artists that ever lived, the Greeks, made their heavens; how shabby it is beside the true heavens, ours!--Poincaré's "The Value of Science," p. 8.
Such language as this is extremely disconcerting to those who hold the popular notion of science and scientists; regarding science as a vague impending mass of solid fact, immutable, inexorable, threatening the extinction of all such things as art, sentiment, poetry, and religion, only to be diverted by a determination to remain ignorant of it; regarding men of science as mere calculating machines, mechanically grinding out logical grist for utilitarian purposes. Mathematical astronomy is surely one of the sciences, the most rigid, remote, and recondite of the sciences. Yet here is the leading mathematical astronomer of the age talking about it as though it were one of the fine arts, a thing of beauty that the artist creates for his own delight in the making of it and shapes in accordance with his own ideas of what is harmonious.
Now we cannot throw out of consideration M. Poincaré's opinion, on the ground that he did not know what he was talking about. A man who has made as much science as he has ought to know how science is made, and what for. To most of us nature--or to avoid hurting our own feelings let us rather say, opportunity--has denied the privilege of knowing this by experience. Consequently M. Poincaré is an especially interesting man to study, for he has been willing to tell us not only what a man of science is, but also how it feels to be one. No other contemporary of equal eminence has been so frank and accommodating in the self-revelation of his methods or so willing to submit himself as a subject of observation. We are admitted to the laboratory of a mathematician, and we can watch the mechanism of scientific thought in action.