How can we know which entities cause mental processes and which entities constitute them? The relevance of this question increased after Adams’ and Aizawa’s objection to the extended mind theory. The article reconstructs some of the arguments in favor of the extended mind theory and of the externalism of consciousness. It then evaluates Kirchhoff’s proposal of a notion of constitution as a relation between levels. There is currently no basic agreement regarding the terms of the controversy, which renders the problem undecidable and weakens both positions alike.