 The earliest view that can be considered an ancestor of functionalism is Aristotle's theory of the soul (350 BCE). In contrast to Plato's claim that the soul can exist apart from the body, Aristotle argued (De Anima Bk. II, Ch. 1) that the (human) soul is the form of a natural, organized human body — the set of powers or capacities that enable it to express its “essential whatness”, which for Aristotle is a matter of fulfilling the function or purpose that defines it as the kind of thing it is. Just as the form of an axe is whatever enables it to cut, and the form of an eye is whatever enables it to see, the (human) soul is to be identified with whichever powers and capacities enable a natural, organized human body to fulfill its defining function, which, according to Aristotle, is to survive and flourish as a living, acting, perceiving, and reasoning being. So, Aristotle argues, the soul is inseparable from the body, and comprises whichever capacities are required for a body to live, perceive, reason, and act. (See Shields, 1990, and Nelson, 1990, for further debate about whether Aristotle's view can be considered to be a version of functionalism.) 