It is my pleasure to be offering the second response to Bill Mattison’s “Aquinas, Custom, and the Coexistence of Infused and Acquired Cardinal Virtues.” The first response, a thoughtful engagement by Dr. Connor Kelly, can be found here

Mattison’s main objective in this essay is to address a lacuna in contemporary Aquinas scholarship. Specifically, Aquinas on the distinction between a disposition to act caused by custom (consuetudo) and a moral habit (habitus) caused by practical reason. According to Mattison, among contemporary moral theologians working to understand Aquinas’s account of the virtues, custom as a source of stable activity has been neglected. Strictly speaking, for Aquinas, a custom is a non-deliberative disposition of our corporeal/sensory faculties to act in a certain way. Trained to constancy and stability through repeated action, acts arising from a disposition of custom (consuetudo) can appear similar to acts that arise from the disposition of a moral habit (habitus); nevertheless, a consuetudo falls short of a habitus in important ways.

In other words, a consuetudo is the actualization of the human being’s natural capacity to “get used to” or to “become accustomed to” consistently performing particular actions in a particular way, a customization which does not arise from practical deliberation about ends and the means to ends (as is the case with a moral habit). For example, a very small child can be trained to wash his or her hands with clinical care before sitting down to eat without understanding the immediate effect or practical purpose of the act—washing our hands in this way is simply what we do before sitting down to eat, it is our custom. 

In recovering the significance of custom in Aquinas, Mattison’s proximate interest is to intervene in the contemporary Thomistic debate on the relationship between the acquired and infused moral virtues. The key question goes like this, how do we make sense of the apparent constancy and ongoing stability of good action in the case of a person who has lost infused moral virtue through mortal sin? Among moralists who affirm the ‘coexistence’ view (as classified by Knobel), such stability is taken to be proof positive that acquired virtue can indeed exist alongside infused virtue in a Christian.

Mattison proposes Aquinas’s account of custom (consuetudo)as an alternative explanation: a stable, non-deliberative disposition to act in a certain way that falls short of acquired virtue. So conceived, a disposition of custom provides a way to understand ongoing good acts after the loss of infused virtue—such that it is not necessary to posit the preexistence of acquired virtue ‘underneath’ infused virtue or propose the spontaneous acquisition of a previously unpossessed moral virtue. This answers one of the more powerful arguments held forth by Thomists who affirm the “coexistence” view of the relationship between the acquired and infused moral virtues.

By my reading, among the more important parts of Mattison’s essay is the care he takes to remind readers of two oft overlooked aspects of Aquinas’s moral psychology and theological anthropology. First, Aquinas’s view that dispositions to act in a certain way (i.e., natural temperament, custom, acquired virtue or vice, and infused virtue) are not capacities in themselves, but qualifications or specifications of underdetermined human capacities toward particular types of action. Second, Mattison reminds his readers of Aquinas’s position on the unity of the intellectual soul (articulated amid the Medieval ‘plurality of forms’ debate). Specifically, Aquinas’s philosophically prosecuted rejection of the quasi-Aristotelian view that the human being possesses multiple souls (i.e., nutritive, sensory, and intellectual souls) and Aquinas’s theologically grounded affirmation that the intellectual soul of the human being is a singular form. For Aquinas, the inalienable aptitude for intellectual apprehension of intelligible truth (the specifying activity of the intellectual soul) is both the essence of each person’s status as the image of triune God and the actualizing principle of the various powers we share with other kinds of terrestrial life (STh I, q. 76, a. 1 & 3; q. 79, a. 8; q. 93, a. 2 & 6; q. 58, a. 3).

Mattison’s latter reminder, concerning the unity of the intellectual soul, is important. Because the intellectual soul is the unifying and integrating form of the specifying act, various potencies, capacities, and accidental qualities of every living human being, any coherently Thomistic account of the distinction between the dispositions of custom (consuetudo) and the dispositions of acquired habit (habitus) cannot prescind from the unambiguously theological principles animating Aquinas’s account of human nature, human dignity, and the two-fold end of the human being. In that way, Mattison cuts off at least two common contemporary mis-readings of Aquinas: First, the problematic tendency to conflate the specifying act of intellect with the derivative intellectual act called the use of reason (See STh I, q. 77, a. 1, ad 7 & a. 5; q. 79, a. 4 & a. 8; q. 93, a. 2 & a. 4; De Veritate, q. 15, a. 1). And, second, moral psychologies that avoid Aquinas’s understanding of the inviolable intellectual nature and contemplative aptitude of every living human being (STh I, q. 93, aa. 4, 7-8; for a detailed engagement on this theme see my essay “Aquinas on Happiness and Those Who Lack the Use of Reason,The Thomist 80 [2016]).

The upshot of the emphasis on those two theological principles is that Mattison’s account of Aquinas on custom is not reducible to the simplistic and problematic claim that ‘the disposition of custom in a human being is identical to the disposition of custom in a brute animal.’ For Aquinas (and as affirmed by Mattison, pp. 9-11), although the sensory powers and appetites of both human beings and brute animals can be conditioned toward the disposition of a custom (consuetudo), that similarity of external cause does not indicate that the quality of custom in human beings and brute animals are identical—and this because the thing qualified in the human being is a power of the intellectual soul. Mattison’s exegetical care and interpretive argument on this point illustrates why Aquinas’s distinction (STh I-II, q. 1, a. 1; q. 18, a. 9) between deliberate “human acts” (actus humanus) and in-deliberate “acts of a human being” (actus hominis) does not amount to the problematic interpretive shorthand that is often taken to follow among some contemporary Thomistic moral theologians.  

In other words, Aquinas rejects the common contemporary interpretative conclusion that there is no meaningful difference between an “in-deliberate act” performed by a human being who lacks the use of reason (e.g., a man with a profound cognitive impairment scratching his beard) and the more-or-less identical act performed by a non-rational, brute animal (e.g., a dog scratching its coat). With respect to the example given, it is true that for Aquinas neither the act of the man nor the act of the dog amounts to a moral act, because in principle neither act proceeds from rational deliberation. However, on Aquinas’s terms, even as the in-deliberate act of a human being does not entail practical deliberation or involve the use of reason, the act remains an intellectual act—i.e., an act that cannot but involve actual knowledge of intelligible truth, insofar as it is an act of a human being.

According to Aquinas, whenever the body passively receives a coordinated sense impression of a material species, the agent intellect abstracts the intelligible form communicated by the phantasm (i.e., that which, if anything, is intelligible of the phantasm) and presents that truth to the possible intellect, by which the human being understands what is perceived (STh I, q. 79, a. 4, ad 5). On Aquinas’s terms, because the rational soul is created with an innate aptitude for knowledge of the first principles of speculative truth, and because the human being is created with an innate desire for knowledge of goodness and truth, any human sensory experience of the material world amounts to actual knowledge—and, thereby, upon sensing, the person possesses a knowledge that is subject to the further, derivative operations of the agent intellect (STh I, q. 79, a. 4; De Veritate, q. 18, a. 8, ad 2; Q. D. De Anima, a. 14, ad 18). Mattison’s argument about Aquinas on the stability of distinctively human customs (consuetudo) fits with what Aquinas has to say about the inalienable contemplative aptitude of persons who lack the use of reason due to an impairment, illness, or injury—in other words, conditions that we usually refer to as ‘intellectual disability’ or ‘cognitive impairment.’

With an eye towards Mattison’s long-term interest in “Aquinas, Custom, and the Coexistence of Infused and Acquired Cardinal Virtues”—i.e., toward the articulation of a broader Thomistic theory of education—there are additional resources in Aquinas’s outlook that Mattison could draw upon to develop his account of consuetudo. For example, Mattison’s reconstruction of the distinction between custom and habit coheres with what Aquinas has to say about the stability of disposition in relation to the sacraments of Baptism, Eucharist, and Confirmation in the case of persons who have lost the use of reason (STh I-II, q. 113, a. 3; III, q. 68, a. 12; q. 72, a. 8; q. 80, a. 9). I look forward to seeing how Mattison might develop these underappreciated aspects of the way Aquinas’s moral psychology and inchoate theory of the disposition of consuetudo cash out in relation to Aquinas’s understanding of the sacraments and persons who lack the use of reason.


William Mattison’s response to this engagement can be found here.