Over the past few decades, a large literature has emerged on the question of how one might unify all or most of psychology under a single, coherent, rigorous framework, in a manner similar to that which unified physics under Newton's Laws, or biology under Darwin's theory of natural selection. It is argued here that this is a highly unlikely scenario in psychology given the contingent and opportunistic character of the processes that brought its original topics together into a new discipline, and the nearly continuous institutional, social, and even political negotiating and horse-trading that has determined psychology's "boundaries" in the 14 decades since. Psychology, as the field currently stands, does not have the intellectual coherence to be brought together by any set of principles that would enable its phenomena to be captured and explained as rigorous products of those principles. If there is a kind of unification in psychology's future, it is more likely to be one that, paradoxically, sees it broken up into a number of large "super-subdisciplines," each of which exhibits more internal coherence than does the current sprawling and heterogeneous whole.