Like science in general, psychological research has never had a method. Rather, psychologists have deployed many methods under quite variable justifications. The history of these methods is thus a history of contestation. Psychology’s method debates are many and varied, but they mostly constellate around two interconnected concerns: psychology’s status as a science, and psychology’s proper subject matter. On the first question, the majority position has been an attempt to establish psychology as scientific, and thus committed to quantification and to objective, particularly experimental, methods. Challenging this position, many have argued that psychology cannot be a science, or at least not a natural one. Others have questioned the epistemic privilege of operationalization, quantification, experimentation, and even science itself. Connecting epistemic concerns with those of ethics and morality, some have pointed to the dehumanizing and oppressive consequences of objectification. In contrast to the debates over psychology’s status as a science, the question of its proper subject matter has produced no permanent majority position, but perennial methodological debates. Perhaps the oldest of these is the conflict over whether and how self, mind, or consciousness can be observed. This conflict produced famous disagreements like the imageless thought controversy and the behaviorist assault on “introspection.” Other recurrent debates include those over whether psychologists study wholes or aggregates, structures or functions, and states or dynamic systems.