But scientists believe that there is a hierarchy of facts, and that we may make a judicious choice among them. They are right, for otherwise there would be no science, and science does exist. One has only to open one's eyes to see the triumphs of industry, which have enriched so many practical men, would never have seen the light if only these practical men had existed, and if they had not been preceded by disinterested fools who died poor, who never thought of the useful, and who were not guided by their own caprice.
What these fools did, as Mach has said, was to save their successors the trouble of thinking. If they had worked solely with a view to immediate application, they would have left nothing behind them, and in face of a new requirement, all would have had to be done again.