 These discussions imply that money is a causal-role kind of some sort. This is questionable, however: such a definition fails to accommodate tokens of money that fail to perform those roles (such as a coin buried in the ground). Instead, money may be better understood as a different sort of functional kind, or perhaps as an artifactual kind (see  section 5.5).  Alternatively, the nature of money may not involve its functions at all. Aristotle (Politics 1.8–10) notes that there are several distinct functions performed by money, each of which would naturally have its own essence; but he points out that we use the same medium for all of these. The money in any given society, he argues, is a product of agreement in that society.