Knowledge is opposed in one way to opinion and in another way to the incapacity for knowledge. Taken in the first way, the “problem of knowledge” is identical to the problem of certitude, i.e. “is it possible for us to attain to some unchangeable/ final/ demonstrated truth?”. This is the problem Descartes famously struggled with in the Meditations, and which had antecedents in Henry of Ghent, Augustine, and Plato. The second problem is the question of what makes the difference between something that knows and something that doesn’t. This is the contemporary problem of knowledge one finds between the Naturalists and those who think that knowledge is an irreducible reality. The Naturalist is striving for the next great unification in science: just as Newton unified heavenly and earthly phenomena, motion and rest; Einstein unified acceleration and gravity; and the modern biologists assume that they have unified the living and the dead, so too philosophers want to accomplish the great unification between things that know and things that don’t. Non-Naturalists have exactly the opposite desire: they want to use non-knowing things as a point of departure to understand knowledge by negation. And so while the two sides disagree about what is true, they have a more profound disagreement of method, and this disagreement goes deeper than the problem of knowledge. The Naturalists see the advance of knowledge as unification and they therefore view any distinction between things as a sign that knowledge is incomplete; and the non-Naturalists, since they see negation as a tool of knowing, see that some knowledge becomes more complete to the extent that the distinction between things becomes sharper and sharper. And so the problem of knowledge is based on a secondary problem of what it means for knowledge to advance.
Hylemorphism suggests one way to harmonize both approaches (the theory of Platonic forms would work too). Hylemorphism consists in the claim that there are two essentially constitutive parts of any natural reality: on the one hand there is a homogenous element that one understands better to the extent that formal distinctions are obliterated; on the other hand there is a formal element that makes one thing understood more clearly to the extend that we divide it from the background of things in which we first experience it as unified. This gives a double approach to any natural phenomenon: one that seeks after “matter”, that is, the dynamic ground where anything can be anything, and the intelligibility of the things has to come entirely from the outside (say, by imposing a mathematical structure) and another that seeks “form” – and knowledge simply is one of the clearest cases in which form rises above the flux and essential unintelligibility of things.