 But one can argue that strong emergentism, at least with respect to some or all mental states, in fact requires a form of substance dualism. On a biological view of emergent thinkers, the micro-physical boundaries of such thinkers may inevitably be vague, for empirical reasons. But it is perhaps doubtful that fundamental causal laws associated with strongly emergent properties would reference vague conditions. The sole apparent alternative is that the properties are instantiated in a distinct, non-vague object instead, as a non-physical mind would be. (See Zimmerman 2010 and Hasker 2016 and, for a reply, O’Connor 2016.)