It now seems to be agreed by those who direct our policy that the development and application of science is of immediate importance to England’s economic welfare. So long as science could be thought of only as a means for the leisurely inception of an Age of Plenty, its benefactions could be postponed without fatal consequences. But we must now be satisfied with lowlier aspirations: science is to lead the state as the Red Queen led Alice—the most rapid progress is necessary with no higher ambition than to remain in approximately the same place as before. We now, therefore, hear a great deal about ‘the scientific method’, for the most part from people who might be quite upset if they were asked just what that method was supposed to be. The scholarly amateur might be heard to mumble something about the Question put to Nature and the experimentum cruris; the scientist speaks of quantitative method and the controlled experiment; the layman is often rude enough to think it no more than common sense. Let us press the question. How does scientific method differ from that used in other sorts of scholarly enquiry? What are the rules for making scientific theories? Just what does science prove? The answers to these questions have been quite widely agreed upon, but are not yet common property; they should be, and this essay is an attempt to make them so. Being no philosopher myself, it goes without saying that in 72what follows I claim proprietary rights only in what may be mistaken.