This chapter raises a problem for the phenomenal concept strategy. The problem is framed partly in terms of the explanatory gap, which is roughly the claim that the existence or nature of phenomenal consciousness cannot be completely explained in physical terms. As applied to the explanatory gap, the phenomenal concept strategy requires a physicalist account of phenomenal concepts on which the gap derives from phenomenal concepts rather than phenomenal consciousness itself. It is argued that to pass muster, such accounts must satisfy the following constraint: that no appeal be made in the explanation to any mental property or relation that is basic. An account violates this constraint if, for example, it makes appeal to an unexplained notion of acquaintance between a subject and her brain states. It is not understood how any physicalist account can both meet this constraint and explain how the explanatory gap derives from the peculiar features of phenomenal concepts. Although some physicalist account might achieve these goals, it is suggested that physicalism may be false not because phenomenal properties themselves are not physical but rather because somehow we embody a relation to them that is itself brute and irreducible to physical relations.
Keywords: phenomenal concept strategy, explanatory gap, physicalism, consciousness, acquaintance