In this paper, I explore the consequences of the thesis that externalism and internalism are (possibly, but as we will see not necessarily, opposite) metaphysical doctrines on the individuation conditions of a thought. If I am right, this thesis primarily entails that at least some naturalist positions on the ontology of the mind, namely the reductionistic ones, are hardly compatible with both externalism and a version of internalism so conceived, namely relational internalism. Indeed, according to both externalism and relational internalism, (...) intentionality constitutes (or at least grounds) the relational content property providing the individuation conditions of a thought, as a relation to an outer or to an inner object respectively. Yet since intentionality turns out to be a modal, hence a nonnatural, property, both externalism and relational internalism deny to thoughts at least token-identity with physical states. Finally, I will give some support to the idea that externalism and internalism must be interpreted as doctrines on the individuation conditions of a thought. (shrink)