Describes the theory that althogh most humans perceive themselves to have a single personality, that in fact a typical mind contains several personalities which often compete to evaluate situations and make decisions.
Although this theory is considered more useful as a psychiatric model, there is evidence that this theory may be be practically substantive in psychology. Most notably is Multiple Personality Disorder (MPD), in which a person loses the ability to recognize a dominant personality, and literally "hears voices." Or, they perform a switch to a different dominant personality based on various triggers.
From a self-developent perspective, this theory has value in understanding why our decision making processes often feel conflicted. We can want something, and don't want it, at the same time. Understanding this reality in our brain helps us to shift to more conscientions decision making.