In 1947 J. Robert Oppenheimer organised a historic conference of physicists at Shelter Island, located off the eastern tip of Long Island, to discuss recent advances in theoretical physics and the direction of future research. Over three decades later, the physics community held another meeting, the 1983 Shelter Island Conference on Quantum Field Theory and the Fundamental Problems of Physics. This volume is the record of the 1983 conference; it also includes much valuable information on the 1947 conference, for which no formal proceedings were ever published. The latter-day conference included many of the participants from the prior event as well as younger physicists who have since become prominent figures in this field. Consequently, this volume is a vital document in the history of physics, of value to students and researchers in many branches of the subject. Topics include the new inflationary universe scenario; supersymmetry; Stephen Hawking's presentation, ""The Cosmological Constant Is Probably Zero""; superunification and the seven-sphere; time as a dynamical variable; induced gravity; and an extensive and previously unpublished paper by Edward Witten on Kaluza-Klein theories. Contributors include Stephen L. Adler, Hans Bethe, M. J. Duff, Murray Gell-Mann, Alan H. Guth, Stephen W. Hawking, Roman Jackiw, Toichiro Kinoshita, W. E. Lamb, Jr., T. D. Lee, A. D. Linde, R. E. Marshak, Y. Nambu, K. Nishijima, John H. Schwarz, Silvan S. Schweber, Steven Weinberg, Victor Weisskopf, P. C. West, Edward Witten, and Bruno Zumino.