In this chapter, the author presents a kind of an Aristotelian philosophy and a Darwinian theory as the confluence affected not only early general psychology but developmental psychology. While academic psychology was struggling to define and establish its conceptual territory, other academic disciplines were also on the make. The tendency to classify and dichotomize did not arise with the advent of the biological and behavioral sciences. The most powerful dichotomy affecting our point of view about human behavior, even infant development, came in the wake of Charles Darwin's theory of evolution—heredity versus environment. The urge to classify, coupled with the determination of the basic or smallest unit of an area of investigation, set the earliest psychologists to classifying activities in terms of: reflexes, instincts, and acquired traits. The author argues the beginning psychoanalytical theories of infancy and early childhood were derived not from investigative studies of infancy but from a process of theorizing backwards from adult aberrant behavior to infancy.