The theories of three philosophers who defend mental substance are considered in this chapter. First is E. J. Lowe, who bases his claim to substance dualism on the fact that persons are substances and that they possess different identity conditions from their bodies, so they must be different substances from their bodies. He admits that this is not a Cartesian dualism and compares his position to P.F. Strawson’s. Second is Richard Swinburne. The core of his strategy is to appeal to split brain scenarios and argue that it makes no sense to think of a subject as being divided in such cases. We may not be able to work out which part of the brain the subject would follow, but we can certainly conceive that it follows one of them because we can conceive of a subject as surviving the loss of any part of its body.Third is John Foster, who thinks that the choice is between bundle and substance dualism. He rejects the Humean bundle theory on the grounds that it does not allow for the fact that we experience our mental states ‘from the inside’, which requires that there be a subject in addition to the elements in the bundle. All three of these philosophers dismiss bundle dualism too easily. They claim to have a non-controversial notion of substance and say that, in that sense, the self or mind is a substance, but one common theory of substance is itself a bundle theory. In particular, the bundle theory of the mind makes use of the notion of the co-consciousness relations between the elements in the bundle and none of them discuss whether the nexus of these relations might give a subjective sense of self.