Functionalism is the view that a mind is defined by ...

"Functionalism is the view that mental states are constituted entirely by their functional roles, rather than by their strict behavioral consequences, or by their physical correlates, or by their immaterial natures."

Functionalism in the philosophy of mind is the doctrine that what makes something a mental state of a particular type does not depend on its internal constitution, but rather on the way it functions, or the role it plays, in the system of which it is a part.