As early as 500 B.C.E., Alcmaeon of Croton identified the brain as the physical seat of the mind. Twenty-five hundred years later, modern science has proven this ancient Greek to be absolutely correct. There is no aspect of psychology that is independent of the brain. The very essence of our humanity—our thoughts, our feelings, our beliefs, and our values—all emerge from this three-pound lump of gray tissue. Psychology has no choice but to take the brain into consideration. Moreover, with the remarkable advances of neuroscience in the last few decades, we now know more about the brain and its relationship to the mind than at any other time in human history.