As part of this basic metaphysical analysis, the Aristotelian tradition thought that the entire corporeal universe was made out of a primordial, prime matter (πρώτη ὕλη, al-hayula al-ula, materia prima). By definition, this prime matter has no form, therefore it is completely potential and unqualified, lacking any structure, actuality, or epistemic content. The problem of prime matter’s knowability arises here: how can something deprived of any sensible and intelligible form be known? Because prime matter is not perceivable, its knowability had to be achieved only indirectly by intellectual reasoning and complex epistemic strategies.

To give an idea of the way that the research is conducted and just how much of a contribution it can make, take the cases of John of Jandun (1280–1328), Walter Burley (1275–1344) and William of Ockham (1285–1347). In his Questions on Aristotle’s Metaphysics (VIII, 1), John of Jandun implicitly criticised the negative strategy (= abstraction of forms from matter) as unable to provide a real understanding of prime matter. It is impossible to conceive abstractly prime matter as separated from the form because prime matter is completely passive and therefore unable to “move the intellect.”

The reason behind the epistemological impossibility to separate matter from form is the same as its ontological impossibility: to be separable from form, prime matter should exist actually, not potentially. Accordingly, Jandun proposes alternative ways through which prime matter can be known: analogy and the consideration of substantial transmutation. In the latter, prime matter is the potential basic stuff that endures when the thing changes into something else, like a golden ring becomes a golden bracelet, or an embryo a baby.

A somewhat similar idea of prime matter as basic neutral stuff is evoked by Walter Burley’s epistemology. In his Commentary on Aristotle’s Physics (I, p. 54), Burley claimed that prime matter can be known by analogy to either artificial/accidental composites or to the form. However, Burley observes that the analogy to the artificial thing offers a better way to conceive prime matter, as it better displays its role as substrate. Considering a golden ring (= artificial composite), for Burley prime matter is considered as performing a function analogous to that performed by the gold of the golden ring, a sort of basic stuff of the thing.

William of Ockham had a somewhat opposite perspective to both Jandun and Burley. In his Summula philosophiae naturalis (I, 9, 180-1), Ockham claimed that prime matter can only be known by its correlation to the form. Indeed, the same relational structure linking together matter and form can be found in every hylomorphic composites. In other words, for Ockham the point is the relational status of matter and form: matter can only be known by form and form by matter. With a more analytical approach than Jandun and Burley, Ockham appears to stress the role of prime matter as substrate of inherence (= what “instantiates” the form) rather than substrate of endurance (= what endures through change).

These examples show that the epistemic strategies adopted by Jandun, Burley, and Ockham were evidently linked to their preliminary ontological considerations of prime matter. However, what does the assumption that matter is knowable by analogy to the form, the composite, or substantial change imply for the ontological and physical theories of matter proposed by these authors? And what epistemological and ontological reasons were behind their choice of one strategy over the others? Initial research suggests a wide plurality of approaches and epistemic strategies in relation to the ontological stakes of the doctrine of prime matter, with different implications.