- Between Actuality and Nonbeing: Prime Matter Revisited
IN HIS COMMENTARY on book I of the Physics, as he takes stock of what has been demonstrated therein, Thomas Aquinas echoes and amplifies sentiments expressed by Aristotle himself: namely, that while a number of difficulties led the ancient naturalists to deny generation, corruption, and a plurality of natural substances, once the nature of matter is made manifest, “all of their ignorance is resolved.”1 That Aristotle’s notion of matter might prove to be so powerful is of course remarkable. Still, even if Aquinas’s appraisal is accurate, it comes, as it were, with a catch. The “enlightenment” that an Aristotelian conception of matter brings about is conditional: the nature of matter removes further ignorance once it is understood. Aquinas evidently assumes that Aristotle has understood matter—if not exhaustively, at least rightly—and that he himself sees what Aristotle saw before him.
Whether their more-or-less shared account is true is a question of great interest, especially to those committed to a nonreductive account of nature, though it is not an issue that I will attempt to adjudicate, at least not directly. Rather, I want to consider, more modestly, whether contemporary interpreters have achieved a sufficiently accurate understanding of the Aristotelian account of matter defended by Aquinas, as the viability of this account first [End Page 547] requires its correct articulation. It may be noted that, even if modest, this aim is only relatively modest, since I am taking for granted that such a conception is notoriously difficult to grasp.
To appreciate this difficulty, I want to direct the present reflection towards Aquinas’s understanding of “prime matter” (materia prima), a notion that he takes himself to be drawing from Aristotle’s physics.2 Insofar as matter, as such, is a principle of potency, and insofar as Aquinas identifies prime matter with pure potency (potentia pura), one of the chief difficulties that besets his conception of matter presents itself in concentrated form in the doctrine of prime matter.3 We might readily understand, for example, how brick and beam, as buildable, are material with respect to a house; but this is in no small part because such materials are in fact actual, qua brick and beam—and, in the natural order, are actual qua stone and wood. But how, we might ask, is something a principle of natural being, and so of real being, when it is, of itself and by definition, “potency alone” (potentia tantum), as Aquinas frequently describes prime matter?4 The [End Page 548] question inevitably imposes itself on the reader of Aquinas, and indeed is something of a cliché. Avoiding the apparent contradiction, however, remains a tall order. One is tempted to hold that the reality “pure potency” aims to pick out cannot be cleanly transposed into the domain of concepts at all. Rather, it can only be interpreted by approximation, and by taking one of two paths at the hermeneutical fork in the road: that is, one seems forced either to accord prime matter some kind of actuality of its own, so as to preserve its reality, or to deny it being altogether, so as to preserve the purity of its mere possibility.
This article seeks to articulate a kind of via media by engaging with two contemporary readings of Aquinas’s account of prime matter. I will begin with Aquinas’s account, chiefly as it is articulated in his On the Principles of Nature. In section II, I will consider two interpretations of Aquinas, each of which represents one of the horns of the dilemma. The first reading, defended by Robert Pasnau, offers what we might call a “reductionist” and “anti-realist” interpretation, since Pasnau denies that pure potency—or, for that matter, materiality in general—designates an existing principle that is really distinct from natural form; natural substances possess no real composition as hylomorphic.5 In contrast to this view, Jeffrey Brower has more recently argued for a “realist” account, in which prime matter is conceived as what he calls “gunky stuff,” an expression technical in meaning, even if colloquial in its formulation. As “gunky stuff,” prime matter is...