In the present article, I develop what I will call the 'perfect duplicate' problem for emergentist views of mental substances. In brief, the problem has to do with the particularity of the mental substance, which requires a metaphysical individuator (not simply an epistemic individuator) that makes me me and does not depend on properties (i. e., universals that are multiply-exemplifiable). Emergentist accounts of minds do not give us a sufficient reason for thinking that this mind is sufficiently distinct from that mind because an emergentist account of individual thisness depends either on properties or on a brute particularity that lacks a sufficient explanation. This is where the emergent mechanism is crucial in precluding the right sort of particularity for the origins of personal identity. Emergentism fails as an explanation for the origins of personal identity, but a traditional variant of a mental substance which is not dependent on a generalizable or universalizable process does not fail, at least not obviously, as an explanation.