We can, however, go a little further, and state that there are points, at least, where Galen attempts to give some more concrete account of what a capacity is or how it works. At Praes. Puls. II.9, 305–6, he states that “the substance (ousia) of a capacity is nothing other than a certain mixture”. And we might relate that formulation to the central, if not definitional, role given to mixture in the account of the soul’s capacities (see §7.2).