In this paper we argue that psychology should be understood as a developmental science, and we place the discipline squarely in the realm of the natural sciences. The case is made that scientific progress in psychology has been (and still is) impeded by prolonged misadventures down conceptual dead ends such as biological reductionism, the nature/nurture debate, evolutionary psychology, and the persistent insistence on emphasizing dependent variables that defy observation and measurement, such as “mind” and cognitive modules. We take issue with the behavior geneticist’s approach to psychology while making the case that many psychologists and biologists today seem wholly unaware of many of the most recent experimental results in the area of molecular genetics, especially as they relate to development. We propose that such results, as well as those in the area of nonlinear dynamics, support a developmental systems perspective of psychology emphasizing the epigenetic nature of development as well as the importance and reality of emergent properties in psychology in particular and science in general. Whereas we do not dismiss the significance of biological processes for a full appreciation of behavioral origins, we understand biology to merely be one of many participating factors for psychology.