It is argued that materialism, the thesis that facts about the mind are reducible without residue to facts about the brain, fails to do justice to the nature of physical phenomena. The symmetry of identity means that if C-fibre firing is just pain, then it can have no properties that pain does not have and cannot, therefore, have any of the objective properties not possessed by pain: it cannot be observable, symmetrically accessible, conceivable from many points of view, spatial, and subject-independent. From this it follows that classic type-identity materialism is false. It does not however follow that supervenience must be rejected, or irreducibly mental properties accepted: subjective mental states might reduce to something lacking the marks of full-blown objectivity; necessary connections between pain and C-fibre firing might exist even though the two cannot be identified.
Keywords: C-fibre firing, identity, materialism, objectivity, pain, subjectivity, symmetry,