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1 See the first two of Aquinas's so-called five ways: Summa theologiae (hereafter, ST), part I, question 2, article 3. (Hereafter references to ST will cite part, question, and article as follows: Ia.2.3. “Ia” indicates the first part [prima pars] of ST, “IaIIae” the first part of the second part [prima secundae], and “IIaIIae” the second part of the second part [secunda secundae].)

2 See Aquinas's Commentary on Aristotle's Posterior Analytics book 1, chapter 4.

3 ST IaIIae.1.4. Translations are my own except where noted.

4 I have discussed these various applications of foundationalist reasoning in various papers. See MacDonald, Scott, “Aquinas's Parasitic Cosmological Argument,” Medieval Philosophy and Theology 1 (1991): 134–73; MacDonald, , “Theory of Knowledge,” in Kretzmann, Norman and Stump, Eleonore, eds., Cambridge Companion to Aquinas (Cambridge: Cambridge University Press, 1993), 160–95; and MacDonald, , “Ultimate Ends in Practical Reasoning: Aquinas's Aristotelian Moral Psychology and Anscombe's Fallacy,” The Philosophical Review 100 (1991): 3166.

5 Aquinas takes the technical term “synderesis” from the tradition. It appears to be a corruption of the Greek “suneisis” (“understanding”). What exactly Aquinas means by it will emerge in Section III below.

6 See, for example, Martha Nussbaum's description of Aquinas's moral theory in Nussbaum, , Aristotle's De motu animalium (Princeton, NJ: Princeton University Press, 1978).

7 My project here requires supplementing with an account of what Aquinas calls the “precepts of natural law.” I intend to undertake that account in another paper.

8 Irwin, T. H., “The Scope of Deliberation: A Conflict in Aquinas,” Review of Metaphysics 44 (1990): 2142.

9 Irwin himself no longer endorses the conclusion he draws in “The Scope of Deliberation.” See Irwin, T. H., “Practical Reason Divided: Aquinas and His Critics,” in Cullity, Garrett and Gaut, Berys, eds., Ethics and Practical Reason (Oxford: Clarendon Press, 1997), 189214; and the chapters on Aquinas in Irwin's forthcoming History of Ethics (Oxford: Oxford University Press).

10 For fuller discussion, see my “Practical Reasoning and Reasons-Explanations: Aquinas's Account of Reason's Role in Action,” in MacDonald, Scott and Stump, Eleonore, eds., Aquinas's Moral Theory (Ithaca, NY, and London: Cornell University Press, 1999), 133–60.

11 Here are three simple examples:

  1. (A)

    (A) intention: to incorporate regular exercise in my life

    • deliberation: walking to work every day would be a good way of incorporating regular exercise in my life; judgment: so I should start walking to work

    • choice: to walk to work every day (or today)

  2. (B)

    (B) intention: to walk to work every day

    • deliberation: if I'm going to walk to work every day, I'll need to get up earlier; judgment: so I should get up earlier

    • choice: to get up earlier

  1. (C)

    (C) intention: to be happy (possess the complete good, live the best life)

    • deliberation: happiness consists in a life containing an appropriate balance of pleasure and virtue; judgment: so I should live that life

    • choice: to pursue a life containing an appropriate balance of pleasure and virtue

12 Aquinas introduces these technical terms at ST IaIIae.11–13. The full discussion in ST IaIIae extends from q. 6 to q. 17. For more detail, see my “Practical Reasoning and Reasons-Explanations.”

13 Aquinas takes the demonstrative syllogism, a particular form of deductive inference, as the paradigm of theoretical reasoning. See my “Theory of Knowledge.”

14 See also ST IIaIIae.47.6.

15 On the nondeductive nature of practical inference, see my “Practical Reasoning and Reasons-Explanations.”

16 Examples A and B in note 11 link together in this way.

17 Example A in note 11 is a case of this sort.

18 See example C in note 11.

19 “We can derive things from the natural law in two ways: in one way as conclusions from its first principles; in a second way as specifications of certain general principles…. The second way is like the way that craftsmen in the course of exercising their skill adapt general forms to specific things. For example, a builder needs to adapt the general from of a house to this or that shape of a house.” ST IaIIae.95.2, trans. Regan, Richard J., Aquinas: Treatise on Law (Indianapolis, IN: Hackett, 2000).

20 “Right practical reason” refers to practical reason that correctly identifies ways of acting that lead to or constitute genuine human good.

21 “The natural law directs human beings by certain general principles … and so the natural law is one and the same for everyone” (ST IaIIae.91.5.ad3, trans. Regan).

“Everybody knows truth to some extent, at least regarding the general principles of the natural law” (ST IaIIae.93.2, trans. Regan).

“We should say that the natural law regarding general first principles is the same for all persons both as to their rectitude and as to knowledge of them” (ST IaIIae.94.4, trans. Regan).

22 These views are developed by Aquinas in ST IaIIae.6–13.

23 Irwin, “The Scope of Deliberation,” 41.

24 As in examples A and C in note 11. Example A is a case in which the end intended is intended under a general description; example C is one in which the end intended is intended under an abstract or formal description.

25 intention: to act in accordance with right reason

deliberationjudgment: right reason requires eating healthily

choice: to eat healthily

intention: to eat healthily

deliberationjudgment: eating healthily requires declining the cheesecake

choice: to decline the cheesecake

26 See previous note.

27 I have inserted the lowercase roman numerals in order to be able to refer to parts of this passage in the discussion that follows.

Irwin translates the passage a bit differently at [ii]: “For temperance aims at this, namely, that a human being should not deviate from reason because of appetites; and similarly, <the aim of> bravery is that a human being should not deviate from the correct judgment of reason because of fear or rashness” (Irwin, “The Scope of Deliberation,” 27–28). Irwin's “namely” in the first half of [ii] renders Aquinas's ut. I take it differently, as introducing a result clause, with “so that.” See the discussion that follows in the text.

28 “It is the law for human beings, which is allotted by God's ordination according to their condition, that they act according to reason” (ST IaIIae.91.6, trans. Regan).

“The virtue of the irascible and concupiscible powers consists of being duly obedient to reason” (ST IaIIae.92.1, trans. Regan).

“Things to which nature inclines human beings belong to the natural law, as I have said before, and one of the things proper to human beings is that their nature inclines them to act in accord with reason” (ST IaIIae.94.4, trans. Regan).

“It is correct and true for all persons that they should act in accord with reason” (ST IaIIae.94.4, trans. Regan).

29 See note 25.

30 See also ST IaIIae.94.3, trans. Regan: “Since the rational soul is the specific form of human beings, everyone has an inclination from one's nature to act in accordance with reason. And this is to act virtuously. And so in this regard, all virtuous acts belong to the natural law, since one's own reason by nature dictates that one act virtuously. But if we should be speaking about virtuous acts as such and such, namely, as we consider them in their own species, then not all virtuous acts belong to the natural law. For we do many things virtuously to which nature does not at first incline us, but which human beings by the inquiry of reason have discovered to be useful for living righteously.”

31 See my “Ultimate Ends in Practical Reasoning.”

I read earlier versions of this paper to the philosophy departments at Purdue University, UCLA, and Texas A&M University, and at a conference at the University of Toronto. I am grateful to the audiences on those occasions for stimulating discussion. I am grateful, too, for helpful comments from the other contributors to this volume, and its editors.

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