Abstract: In recently work, Schaffer attempts to argue that the classic explanatory gap in philosophy of mind is the general problems as the epistemic opacity of across layers of reality at different levels. He believed that all the gaps could be bridged by the metaphysical grounding principles. We will refute Schaffer’s argument and further defend the specificity of the problem of consciousness explanatory gap. Finally, we argue that truly bridging the explanatory gap of consciousness requires explanatory knowledge that answers both epistemological and metaphysical questions.

Key Words: Explanatory gap; Grounding; Mereological gaps; Explanatory knowledge