 Potential problems for the epistemic strategy include: (1) whether it can be applied to nonhuman animals, many of whom presumably also have contentful mental states; (2) whether a canonical language that satisfies the necessary constraints is possible (see e.g. Schroeter 2004; Soames 2005, pp. 216–218; Sawyer 2007); and (3) whether a version of the “what is held constant” problem for the diagonalization strategy also poses problems for the epistemic strategy. (This last point is discussed a bit further in section 6.2.)