The problem in the philosophy of science which interests me beyond all others is that of constructing an abstract deductive system isomorphic with the theory of the natural sciences. Clearly, this task must be the work of many years and many minds. Some portions of it have already been accomplished; but a great deal remains to be done, and the difficulties of the problems yet unsolved impress me as formidable. I believe, however, that it would be hard to overestimate the benefits which might follow from the construction of such an abstract theory, always provided that that theory met certain conditions. Not only must the system in question measure up to the standards of rigor and precision set by the logicians, but it must also be cast in such form that a working scientist could learn to understand at least that part of it applicable to his own specialty without being forced to drop his professional work and devote the labor of years to mastering the subject.