This would lead to something like:
Jpfc: S’s belief B is justified iff (i) S does not take B to be defeated, (ii) the cognitive faculties producing B are (a) functioning properly, (b) truth-aimed and (c) reliable in the environments for which they were ‘designed’, and (iii) the production of B accords with the implicit conceptions of the concepts making B up.In certain cases, perhaps involving simple logical inferences, the innate cognitive faculties would themselves encode the relevant implicit conceptions, and so clause (iii) would be redundant. But in more advanced situations, where we think about electrons or groups, clause (iii) would come into play. As far as I can tell, this proposal would allow for justified beliefs in demon worlds. For example, if an agent was in a world where groups had been destroyed (if we can make sense of that metaphysical possibility), her group beliefs could still be justified. In fact, the main objection that I foresee to this proposal is that it makes justification too easy, but presumably that is also an objection that the proper function proposal faces for analogous cases.