Reber believes he has simplified Chalmers’s “hard problem” of consciousness by arguing that subjectivity is an inherent feature of biological forms. His argument rests on the related notions of continuity of mind and gradual accretion of capacities across evolutionary time. These notions need to be defended, not just asserted. Because Reber minimizes the differences in mental faculties among species across evolutionary time, it becomes easier to assert, and perhaps believe, that sentience is already present in early biological forms. The more explicit we are about the differences among these mental faculties and the differences across species, the less persuasive is Reber’s claim of the mental unity of species. The further claim that mental...