" In all things which have a plurality of parts, and which are not a total aggregate but a whole of some sort distinct from the parts, there is some cause ; inasmuch as even in bodies sometimes contact is the cause of their unity, and sometimes viscosity or some other such quality.But a definition is one account, not by connection, like the Iliad, but because it is a definition of one thing. "

― Aristotle , Metaphysics