 Hilary Putnam introduced multiple realizability into the philosophy of mind. Challenging the “brain state theorists”, who held that every mental kind is identical to some yet-to-be-discovered neural kind, Putnam (1967) notes the wide variety of terrestrial creatures seemingly capable of experiencing pain. Humans, other primates, other mammals, birds, reptiles, amphibians, and even mollusks (e.g., octopi) seem reasonable candidates. But then, for the “brain state theory” to be true, there must be some “physical-chemical kind” common to this wide variety of pain-bearing species, and correlated exactly with each occurrence of the mental kind. (This is a necessary condition of the hypothesized type-identity.) Biological considerations speak intuitively against this requirement. Neuroanatomy differs across terrestrial brain-bearing creatures, especially at systems and circuit levels; function, especially sensory functions, are increasingly “corticalized” as cortical mass increases across species. Convergent evolution generates similar phylogenic traits in organisms not closely related due to their having to adapt to similar environments or ecological niches. Such realizers of the same function will highly likely be distinct “physical-chemical” kinds.