 By classifying “man” with other organisms and then drawing a distinction between organisms and persons, Locke recognizes that he is prying apart the traditional notion of “man” as rational, on the one hand, and animal, on the other. Against this traditional understanding, he introduces a thought experiment involving a rational parrot (II.xxvii.8). Our unwillingness to call this parrot a “man” simply because it is an animal possessed of language and reason illustrates that not all rational animals are men. Nor are all men rational animals: “whoever should see a Creature of his own Shape and Make, though it had no more reason all its Life, than a Cat or a Parrot, would call him still a Man” (ibid.).  The human/person distinction gains traction once it is coupled with one of the Essay’s key insights, viz. that sortal concepts (e.g., human animal, person) are often (though not always) associated with different identity criteria. “Identity”—as he puts it in the title of the section in which this insight is first registered—is “suited to the Idea”: “such as is the Idea belonging to [a] Name, such must be the Identity” (II.xxvii.7). Locke is keenly aware of the significance of this principle; “if it had been a little more carefully attended to”, he admonishes, it “would possibly have prevented a great deal of that Confusion, which often occurs about this Matter … especially concerning Personal Identity” (ibid.).  And indeed, it is this insight about the association of sortal concepts and identity criteria that encourages the thought in Locke that human animals and persons are governed by different criteria of identity. Whereas a human animal persists just in case “the same continued Life [is] communicated to different Particles of Matter, as they happen successively to be united to that organiz’d living Body” (II.xxvii.8), when one “consider[s] what Person stands for”, Locke contends, one finds that its persistence consists in “the sameness of a rational Being”. He explains: “as far as this consciousness can be extended backwards to any past Action or Thought, so far reaches the Identity of that Person” (II.xxvii.9).