This article proposes a theory whereby the physiological changes induced by placebos are accompanied by corresponding changes in the patients mental state. The author begin by defining the placebo problem, and review the three leading theoretical approaches for solving it meaning theory, expectancy theory, and conditioning theory before discussing the significant theoretical issue posed by a classic case of placebo immunosuppression in rats. The theory of full correspondence is then introduced as a way of explaining the nature of the placebo effect and of resolving the conflict between meaning-oriented and mechanism-oriented approaches to the phenomenon. After proposing how to test the theory experimentally and examining existing evidence for it. The author consider its ability to integrate the dominant theoretical perspectives of the placebo effect within a framework centered on the patient's subjective experience, the one variable overlooked on both sides of the meaning/mechanism divide.