The notion that askēsis is as much additive as privative is central to Foucault’s larger discussion of the term. Readers will recognize a connection with Hadot when Foucault writes, “This is a work of the self on the self, an elaboration of the self by the self, a progressive transformation of the self by the self for which one takes responsibility in a long labor of ascesis (askēsis).” Foucault also speaks of askēsis as “converting to oneself” through abstinence, meditations on death, trials of endurance, and self-examination, and as a question that asks, “What working practice is entailed by conversion to the self?”
Edward McGushin has written a very helpful book in this area titled simply Foucault’s Askēsis. This text makes clear that Foucault’s later work on the theme of care of the self is essential to his understanding of ascetic practices. McGushin writes, “Care of the self is therefor an askēsis, an exercise through which one becomes a subject.” In addition to positioning care as a practice of the self, McGushin also emphasizes how askēsis results in an addition to the subject. One sees here the link between theory, or discursive knowledge, and the effect it has on the formation of the person. “Knowledge of things, of the world, is a spiritual practice insofar as it transforms the self,” is McGushin’s way of putting it, as he recounts how listening, reading, writing, and speaking are also modes of ascetic practice. Mēlētē, or solitary, meditative exercise, in this case, is another example McGushin gives, which again points to the recursivity inherent to ascetic practice. McGushin writes, “In a meditation the subject is transformed, put to the test, and is, in a sense, at the mercy of the thoughts she thinks.”
As with Hadot’s understanding, Foucault marks a link between philosophy, or “the form of thought that asks what it is that enables the subject to have access to the truth and which attempts to determine the conditions and limits of the subject’s access to the truth,” and spirituality, or “the search, practice, and experience through which the subject carries out the necessary transformations on himself in order to have access to the truth.” Here Foucault lists purifications, ascetic exercises, renunciations, “conversions of looking,” and “modifications of existence” as specifically spiritual exercises. His discussion of askēsis emerges within this confluence of philosophy and spirituality.
A specific example that Foucault takes up in his text is the practice of epistrophē, which he variously describes a reversion, a recollection, a turning away from appearances, or an acknowledgement of one’s own ignorance. As I noted earlier, the structure of an ascetic practice can be similar across schools that hold wildly different metaphysical commitments — in, for example, the different ways the meaning of the self’s relation to itself is rendered in Aristotelian, Plotinian, Kantian, and Christian monastic contexts — whilst still operating with a more or less isomorphic understanding of how to execute a practice.
Epistrophē is one of these practices. As Foucault notes, the notion of “turning away” from the world of appearances is present in Platonic and Hellenistic-Roman versions of epistrophē, while the meaningof such a turn is quite different in each philosophical context. The Platonic epistrophē involved a practice of recollecting one’s “ontological homeland” (of truth, essence, Being, and so on), while the Hellenistic-Roman epistrophē had a much more immanent character, advocating not for a turning toward another, truer world outside of this one, but for a freedom achieved through turning away from appearances in the here and now.
Certainly, the emphasis on purification, renunciation, and epistrophē calls to mind ascetism’s privative side, but even here Foucault is clear that this meaning does not account for the complex scope of ascetic practice. He writes,
We [modern peoples] understand ascesis as progressive renunciations leading to the essential renunciation, self-renunciation. We hear it with these resonances. I think ascesis (askēsis) had a profoundly different meaning for the Ancients. First of all, because obviously it did not involve the aim of arriving at self-renunciation at the end of ascesis. It involved, rather, constituting oneself through askēsis.
Askēsis is related here to the “self-transfiguration that is the happiness one takes in oneself.” This, says Foucault, was “the objective of askēsis.”
The sense I take from these passages is that askēsis may often involve renunciation of some kind, and in that sense it does point to a kind of rejection, but this act should be understood as a productive rejection. In other words, something new is acquired through the deployment of renunciation. Foucault continues, “In two words, ancient ascesis does not reduce: it equips, it provides.” What does it provide? Foucault answers, it provides paraskeuē (in Greek) or instructio (in Latin). Foucault describes paraskeuē as “both an open and an oriented preparation of the individual for the events of life.” It is in the nature of askēsis to deliver and install new capacities as one withdraws from old habits and behaviors.
Foucault continues, “In the ascesis, the paraskeuē involves preparing the individual for the future, for a future of unforeseen events whose general nature may be familiar to us, but which we cannot know whether and when they will occur.” The image of the athlete returns in this context. The athlete, suggests Foucault, is the one who practices a certain kind of askēsis, to acquire paraskeuē, which can also imply an internalization of a certain logos, “or a rationality that states the truth and prescribes what we must do at the same time.”
These logoi — the sense here is that we internalize many of them — are important for Foucault, “They are inductive schemas of action, which, in their inductive value and effectiveness are such that when present in the head, thoughts, heart, and even body of someone who possesses them, that person will then act as if spontaneously.”Askēsis is in this sense not a practice opposed to understanding, but is in fact a practice that through its execution delivers understanding. One learns through ascetic practice. Foucault continues, “So, these material elements of rational logos [e.g., written instructions or examples] are effectively inscribed in the subject as matrices of action. This is paraskeuē. And the aim of the askēsis necessary to the athlete of life is to obtain this.”Askēsis, then, is productive of such matrices of action, matrices that just are the body’s reorganization into new modes of being, into new modes of perception, which amounts to the same thing. Perception and being are integrally related through askēsis,a theme I also see pronounced in the work of Peter Sloterdijk.
 Foucault, The Hermeneutics of the Subject, 16.