Publisher Summary Every young science goes through a number of stages in its development from naturalistic observation—through the detection of areas of lawfulness and the construction of more limited theories—to more comprehensive, parsimonious, and elegant theories. For philosophers of science, the history of psychoanalysis provides a unique opportunity to study the evolution of a science. Psychoanalysis has a special history, because it was dominated so long by Sigmund Freud, a man of great genius—who made most of the observations upon which psychoanalysis is built. To proceed with an assessment of the status of psychoanalysis as a science of current day, some choices have to be made. The chapter discusses what the analysts call their metapsychology rather than their theory and the technique of psychoanalytic treatment of patients. It has also been found that the status of the dynamic-economic metapsychology of contemporary psychoanalysis is very provisional. For philosophers of science, the history of psychoanalysis provides a unique opportunity to study the evolution of a science.