Kantor was interested in a wholly naturalistic approach to scientific activity in general, and the science of psychology in particular. As a philosophy of science, interbehaviorism characterizes all scientific activities from a naturalistic foundation (Kantor, 1953; Kantor & Smith, 1975). As a scientific system interbehavioral psychology is an organized enterprise, coordinating all scientific activities through the detailed procedure of system building (Kantor, 1958). Kantor was a scholar of Renaissance proportions and his achievements were truly extraordinary. Unfortunately, his work and its implications for science and for the science of psychology in particular have often been overlooked or misunderstood. In this chapter we attempt to outline some of the unique features of both the philosophy of interbehaviorism and the scientific system of interbehavioral psychology. We will begin with an overview of interbehaviorism as a ­philosophy and conclude with the systemic details of interbehavioral psychology.