The correspondence hypothesis is a conjecture to the effect that psychological phenomena correspond (in one-to-one fashion) to certain states and processes in people's brains. It suggests that for each and every (different) psychological phenomenon there is a different brain state or process with which it is uniquely correlated. [1] This hypothesis, often referred to in philosophical literature as "The Principle of Psycho-Physical Isomorphism," is purported to provide the empirical foundation on which a variety of conflicting mind-body theories are constructed, as well as the source of the "riddle" which such theories aim to unravel. [2]