ABSTRACT
Questions of principle are sometimes regarded as too unpractical to be important, but I suggest that that is certainly not the case in our subject. The range of phenomena that we have to deal with is so broad that, were it to be dealt with wholly at the technological or practical level, we would be defeated by the sheer quantity and complexity of it. The total range can be handled only piecemeal; among the pieces are those homomorphisms of the complex whole that we call “abstract theory” or “general principles”. They alone give the bird’s-eye view that enables us to move about in this vast field without losing our bearings. I propose, then, to attempt such a bird’s-eye survey.
