For Aquinas, the very meaning of perfection demands that there could be no absolute perfection that was not shared by three Persons. My first aim in this paper is to establish this point, which has been acknowledged only rarely by readers of Thomas, yet which follows unavoidably from Thomas's theology of the Word. I show as much by engaging with scholars who, rightfully attentive to Thomas's teaching on faith and reason, and to his rejection of “necessary reasons” for the Trinity, deny or fail to recognize this link between the meaning of perfection and the necessity of the Trinity. Such scholars, however, all end up running aground on claims that Thomas consistently registers. I hope to show, therefore, that new approaches to this area of Thomas's Trinitarian thought are needed: approaches that can acknowledge his presentation of perfection as necessarily Triune without violating the limits he places on natural reason.
