 The traditional package specifies a set of conditions some or all of which substantial claims about “human nature” are supposed to meet. Before we turn to the systematic arguments central to contemporary debates on whether such conditions can be met, it will be helpful to spend a moment considering one highly influential substantial claim. Aristotle’s writings prominently contain two such claims that have been handed down in slogan form. The first is that the human being (more accurately: “man”) is an animal that is in some important sense social (“zoon politikon”, History of Animals 487b; Politics 1253a; Nicomachean Ethics 1169b). According to the second, “he” is a rational animal (Politics 1523a, where Aristotle doesn’t actually use the traditionally ascribed slogan, “zoon logon echon”).