 A significant difference between Collins and Locke…is that Collins thought that material systems provided a better explanatory basis for consciousness, which changes the probability calculus. Collins provides evidence that casts doubt on Locke’s claim that “it is in the highest degree probable” that humans have immaterial souls. Although he is building from a Lockean starting point, namely the possibility that God might superadd thinking to matter, he ends up with a naturalized version: thinking “follows from the composition or modification of a material system” (Clarke and Collins 2011: 48). (Jorgensen forthcoming) 