Had I been asked any time last century to discourse to philosophers on a subject entitled “Beyond Physics,” I should have taken it as meaning “Metaphysics,” and have declined on the ground that they knew more about it than I did. But now that the subject has been suggested to me in the second quarter of the twentieth century, I realize that a certain number of physicists, especially mathematical ones, have gone beyond themselves in a semiphilosophical direction, have thrown our old physical ideas into some confusion, and have devised a number of complicated abstractions which they seem able to deal with by recondite methods invented for other purposes by the pure mathematicians. Of these they do not attempt to form any mental image, and do not encourage us to try to do so. They mistrust the method of physical imagery, or what they call “models,” which constituted one of the main methods of investigation in the nineteenth century; they are content to deal with abstract symbols, which presumably represent something real, though they mistrust the term “reality,” and decline to define it. The younger modern physicists are content to work in a nebulous region of unknown and perhaps unknowable entities, remote from our ordinary conceptions and everyday experiences; so that, whereas the old idea of explanation consisted in trying to express mysterious or recondite phenomena in terms of something with which we were more familiar, they now point out that our apparent familiarity with those simpler things was more or less of an illusion, that they furnished no valid explanation at all, and that the physical and engineering conceptions or habits of thought on which we depended were largely misleading.