How can Being be Limited?: W. Norris Clarke on Thomas’s “Limitation of Act by Potency”

Fr. Norris Clarke's 1952 paper on Thomas Aquinas's limitation of act by potency continues to be one of his key interpretive papers on Thomas. It articulates Thomas's position on being as a synthesis of the Neoplatonic and Aristotelian traditions, and gives a strong reading of the centrality of the act of existence in Thomistic metaphysics. Central to the account is Clarke's commitment to a 'thin essence' view, where essence is understood simply as potencies limiting act. Precisely what it means, however, for potencies (that is, a particular kind of non-being) to do anything is less than fully clear. This paper attempts to clarify Clarke's position by comparing it with Stein's alternative understanding of essential being—in contrast to Thomistic potencies—as limiting actual being.