Metaphysical naturalism (in the philosophy of mind) is the thesis according to which mental states can be reduced to, and thereby explained by, neurophysiological states. In this paper I discuss whether this thesis is plausible taking into consideration different kinds of mental states: propositional attitudes, on the one hand, and phenomenal states, on the other. I shall argue that, while metaphysical naturalism is false for standard propositional attitudes (beliefs, desires etc.), it can be defended in the case of low-level phenomenal states, or raw feelings. As a consequence, since the instantiation of high-order mental states requires the neurophysiological mechanisms that constitute raw feelings, the notion of self has a biological basis, and in this sense, we can speak of a “natural self”. The structure of the paper is the following. In the first paragraph I shall focus on the naturalization of paradigmatic intentional states (beliefs and desires). In the second paragraph I move to the discussion of raw feelings and show the consequences of my view for the notion of self.