[1] This argument is located in Summa Contra Gentiles, henceforth SCG, at I.13.17–32: St. Thomas Aquinas, Summa Contra Gentiles, Vol. I, Tr. Anton C. Pegis, (Notre Dame, IL: University of Notre Dame Press, 1975): pp. 90–95.

[2] Norman Kretzmann, The Metaphysics of Theism: Aquinas’s Natural Theology In Summa Contra Gentiles I, (New York: Oxford University Press, 1997): p. 61.

[3] E is rendered by Thomas in several ways: ‘every mover is moved…’ SCG I.13.17, line 2, p. 90., or, ‘every mover is moved by another’ SCG I.13.17, line 13, p.90. I take these varying locutions as different formulations of the same principle encapsulated by E.

[4] Thomas speaks, for example, of a proposition being true per accidens or per se, of motion occurring per accidens or per se, and also of impossibility and contingency as related concepts. It seems easiest to think of the distinction in terms of accident and essence – but these terms themselves must be explicated further – and that is beyond the project of this paper.

[5] Kretzmann, p. 68.

[6] This point can be made more formally with M standing for the predicate ‘is a mover’ and V for the predicate ‘is moved by some distinct object.’ E, then, is the universal claim that (∀x)(Mx ⊃ V x). A state of affairs in which E does not obtain is simply one in which (∃x)(V x ∙ Mx).

[7] This of course is not to suggest the ‘telescope’ model of possible worlds ontology criticized by Kripke. See Saul Kripke, Naming and Necessity, (Cambridge, MA: Harvard University Press, 1980), p. 44.

[8] For an extended defense of the agent-causal libertarian account, see Timothy O’Connor, Persons and Causes: The Metaphysics of Free Will, (New York: Oxford University Press, 2000).

[9] Peter van Inwagen, An Essay on Free Will, (New York/Oxford: Clarendon Press/Oxford University Press, 1983): p. 91.

[10] This author, for example.

[11] Kretzmann, p. 68.

[12] Lest I overstate my case for argument M, I note that each premise of argument M may very well turn out to be problematic. At the least, though, M presents a prima facie challenge to the conjunction of P8 and P9. Thomas may turn out to be victorious, but, absent any further argument, I take myself as justified in believing M over the conjunction of P8 and P9.

[13] I note that this counterexample functions, not merely as a possible counter-instance to a claim like P6. Instead, it is something that occurs in the actual world. Thus, regardless of the modal status of P6, it falls prey to the tea-kettle counter-example.

[14] They may, in fact, even exhaust the reader.

[15] Kretzmann, p. 78.

[16] Ibid., p. 77.

[17] Ibid., p. 83.

[18] This directly calls into question C1, C2, C3, and C4, and indirectly, every other conclusion in G2 (by keeping a denial of E as a live possibility).

[19] I say this, of course, with the trepidation due any disagreement with Thomas, keeping in mind the apt advice of Freddoso that ‘…without the sort of systematic study that we are not generally trained for either linguistically or philosophically, we contemporary Christian philosophers are not in a position even to understand, much less to criticize intelligently, most of the work of… classical metaphysicians. For in order to grasp what these authors are saying, we must immerse ourselves in their works and, at least initially, humbly submit ourselves to their tutelage; but this is a project that most of us have neither the expertise nor the time nor the inclination to undertake.’ Alfred J. Freddoso, ‘The Openness of God: A Reply to William Hasker,’ Christian Scholar’s Review 28 (1998): pp. 124–133.