The notion of reality in the physical world has become, during the last century, somewhat problematic. The contrast between the simple and obvious reality of the innumerable instruments, machines, engines, and gadgets produced by our technological industry, which is applied physics, and of the vague and abstract reality of the fundamental concepts of physical science, as forces and fields, particles and quanta, is doubtlessly bewildering. There has already developed a gap between pure and applied science and between the groups of (...) men devoted to the one or the other activity, a separation that may lead to a dangerous estrangement. Physics needs a unifying philosophy, expressible in ordinary language, to bridge this gulf between "reality" as thought of in practice and in theory. I am not a philosopher but a theoretical physicist. I cannot provide a well balanced philosophy of science that would take due account of the ideas developed by differing schools, but I shall endeavor to formulate some ideas which have helped me in my own struggle with these problems. (shrink)