What Is Multiple Realization?
Thomas W. Polger · Oxford University Press eBooks · 2016
The idea of multiple realization begins with a simple thought: There exists sameness of kind at one level of description, and differences in kind at a lower level of description. Two organisms, for instance, might be described as sharing a perceptual state, while differing in the physical states that realize this state. When investigating the possibility of multiply realized psychological states, one cannot confuse psychological similarity with behavioral similarity, as one might when investigating whether a capacity like face recognition might be multiply realized. Two kinds of organism might be able to recognize faces, but only one (or neither!) might do so through psychological means. The shared behavior is thus not evidence of a multiply realized psychological process. Finally, modal intuitions regarding the possibility of multiple realization do not come for free. They should be grounded in what our best sciences tell us about the prospects for actual multiple realization.