St. Thomas and the Analogy of Potentia Generandi

The Thomist 64 (2000): 581-92 ST. THOMAS AND THE ANALOGY OF POIENTIA GENERANDI JOHN F. BOYLE University ofSt. Thomas St. Paul, Minnesota In the intellectual achievement that is St. Thomas Aquinas's Trinitarian theology, the question of whether the potentia generandi-the power of generating-is essential or personal occupies a rather modest corner. The question is not, however, without interest, for it is one on which Thomas changes his mind. Such questions, even the modest ones, offer their own particular insights into Thomas's thought. The question itself is an interesting one. In the life of the Trinity, the Father generates the Son. The act of generation is a personal act of the Father; as such, it is proper to the Father but not to the Son or the Holy Spirit. The act is a notional act, that is, an act that makes known something proper to a particular divine person. But acts do not come from nowhere: some agent must do the act, and that agent acts on the basis of powers that he has. The agent in this case is the Father. But what about the power of generating (potentia generandi)1 by which he acts? Is it essential or personal? The answer is not obvious. Agents in the created order act on the basis of powers they have according to their nature or essence; acts are of persons, but the power is essential, that is, according to the person's nature. Thus one might be inclined to say that the potentia generandi is essential, a matter of the divine nature. Yet in the case of the Trinity, in 1 Thomas usually speaks of potentia generandi but sometimes of potentia generativa; he seems to use these terms interchangeably. 581 582 JOHN F. BOYLE which the three persons share one nature entirely, if the power were essential, then would not the Son and the Holy Spirit share that power and be able to generate too? Thus one might be inclined to say that the potentia generandi is proper to the Father, that is to say, it is personal and not essentiaL2 This question is not new with St. Thomas. It is found in this particular guise in the twelfth century. Peter Lombard attends to it in his Liber sententiarum where he holds that the potentia generandi is essential.3 Once in this standard textbook of theology, the question was assured a life; it is found in almost all-if not all-of the Trinitarian literature of the thirteenth century, and indeed in the Scholastic literature well beyond.4 Thomas inherits the question. Although it is not at the heart of his Trinitarian theology, he keeps coming back to it and reformulating his answer to it. The question nagged not because doctrinal fidelity hung in the balance, but because it demanded particular refinement and precision in analogical analysis. The general contours of St. Thomas's development on this question are dear. The question admits, as Thomas always notes, of three possible answers: the potentia generandi is purely personal, purely essential, or both personal and essential. When he first addresses the question in his Parisian Scriptum on Lombard's Liber sententiarum, he maintains what we might call a strong middle position, that is to say, that the potentia generandi is equally essential and personal. He considers the question again a number of times during his sojourn in Rome 2 The difficulty is captured well by John of St. Thomas, In primam parlem Summae theologiae, disp. 36, a. 3, from his Cursus theologicus (Paris: Desdee, 1946), vol. 4, fasc. 2, pp. 330-31. This was in the early printed editions disp. 16 of Cursus theologici in Primam Partem D. Thomae Tomus Secundus, a quaestione decima quinta usque ad vigesimam septimam. 3 Peter Lombard, Sententiae in N libris distinctae, I, d. 7, c. 2, ed. Patres Collegii S. Bonaventurae (3d ed.; Grottaferrata: Editiones Collegii S. Bonaventurae, 1971), vol. 1, pp. 93-94. 4 Banez gives a concise and systematic summary of the various Scholastic answers to the question in his commentary on Summa theologiae I, q. 47, a. 5 in Scholastica commentaria in universam primam parrtem (Venice: Apud Petrum Mariam Bertranum...