Foucault's interpretation of Descartes' thought runs through his academic career, appearing sporadically in his early works such as History of Madness, Mental Illness and Psychology, and The Order of Things, where Descartes mainly serves as the intellectual background for examining the phenomenon of madness and the history of reason, pointing out that Descartes transformed reason from "ethics" to "natural essence." Between 1966 and 1972, Foucault further analyzed the rational characteristics of the cogito subject, though scholars criticized him for neglecting the complexity of Descartes' thought. In the 1980s, late Foucault regarded philosophy as the ascetic practice of "care of the self," explicitly proposing the "Cartesian moment" thesis in his Collège de France lectures, viewing it as a crucial turning point in Western philosophy and elaborating in detail on the deep connotations of reason as ethics and thinking as ethical practice. Foucault believed that the Cartesian moment replaced the ancient imperative of "care of the self" with "know thyself," shifting the foundation of access to truth from spiritual exercises of the self to the essence of the subject; yet his late thought still emphasized that the foundation of the subject-truth relationship lies in ascetic practice, with "reason as ethics" being precisely the experience of this practice.

The History of Madness and the Birth of the Cogito Subject

This section elucidates Foucault's historical analysis in History of Madness of the evolution of Western conceptions of madness from the 15th to the 17th century. Two approaches to thinking about madness existed in the 15th and 16th centuries: the visual arts presented madness as a cosmic tragic experience, while moralists viewed it as moral defect and error of reason. The latter gradually became dominant from the 16th century onward; madness was incorporated into a moral framework, serving as a warning against human narcissism and vanity, with reason and unreason in a dialectical relationship. A crucial rupture occurred in the 17th century: reason and unreason were clearly separated, madness was expelled from the domain of truth, and reason acquired self-evident certainty. Foucault discovered in Descartes' Meditations the prototype of this new subjective practice—the rational subject confirms itself through autonomous exercise, while madness is merely an external object scrutinized by consciousness, with unreason no longer internal to reason. This transformation marks the birth of the "cogito" subject: the subject belongs to the category of reason, possesses the privilege of accessing truth, and thereby acquires the right to govern "man." The chapter ultimately points toward a reinterpretation of Cartesian thought as a strategy of resistance, revealing the apparatus of power, knowledge, and subjectivity behind it.

The Performativity of the Text: My Body, This Paper, This Fire

This section discusses Foucault's unique approach to reading Descartes' Meditations, with the core insight of treating the text as an "exercise" and ascetic practice rather than mere logical argumentation. Responding to Derrida's criticism, Foucault analyzes in depth why Descartes rejected madness as legitimate grounds for doubting the senses while accepting dreams as a means of doubt. Foucault points out that "madmen" (amentes) and "demented" (demens) in Descartes' text have a legal character, referring to those deprived of religious, civil, and judicial capacity; if a subject recognizes himself as mad, he simultaneously loses the right to systematic meditation and to communicate that meditation to readers. This contrasts with the tradition of Montaigne and Erasmus, where madness is seen as a possible path to truth. Foucault further reveals that the Meditations contains two discursive procedures: "demonstrability" and "exercisability"—the former follows rules of reasoning, while the latter appears as a self-technique that transforms the subject's mode of being. The hypothesis of the dream belongs to the latter; it allows the subject to place itself in a specific situation through thought, thereby deviating from its original state. Though madness and dreams are equally effective in disrupting sensory experience, the dream, as "an exercise that anyone can perform," is more practical and thus chosen by Descartes as a technique of doubt. Foucault emphasizes that the essence of "meditation" is a game that thought plays upon the subject, rather than a game that the subject plays with thought; this interpretation reveals how Descartes achieves a new experience of subjectivity through self-practice.

Dream and Meditation as Technologies of the Self

This section examines Descartes' use of the dream as a philosophical practice of self-technique rather than as a propositional argument, analyzing how the hypothesis of the dream achieves the transition between doubt and certainty by transforming the mode of being of the meditating subject. The key distinction between dream and madness lies in that the dream preserves the subject's critical capacity and qualification to speak the truth, while madness deprives one of this right; the dream allows the subject to enter a virtual state thereby overcoming obstacles of reality, whereas madness binds one to false appearances. The author further elucidates the functional homogeneity between the hypothesis of the "evil deceiver" and the dream—both enable the subject to detach from identification with any appearance, rather than mistaking false images for reality as the madman does. Meditation on the dream not only transforms the subject's mode of existence, leading it from darkness to light and from mixture to purity, but also constitutes a system of reality in the sense of "apparatus," a system that determines Descartes' mode of being as a cognitive subject and his relational patterns with self, world, and others. Ultimately, this self-technique gives birth to a new autonomous subject, which acquires the "right to truth" through care of the self and ethical parrhesia, thereby replacing the subjectivity model under Christian pastoral power.

Traditional Rupture and the Return of Asceticism

This section explores the double positioning of Descartes' Meditations in Foucault's thought: both within the ancient ascetic tradition of the Western subject-truth relationship and inaugurating a modern rupture external to that tradition. Foucault points out that through the self-technique practice of "meditation," Descartes purifies the mind, making the subject capable of knowing truth; yet his result replaces "exercise" with "evidence," and the transformation of way of life with methodological evidence, thereby establishing a non-ascetic model of the knowing subject. This "Cartesian moment" causes philosophy to shift from the "spirituality" model to the "knowledge-cognition" model, making the institutionalization of modern science possible. However, Foucault simultaneously emphasizes that Descartes' project itself was a movement of resistance: he attempted to liberate the individual from Christian pastoral power, to criticize illegitimate relations of manipulation through reshaping subjectivity, and to reestablish the foundation of philosophical parrhesia. Thus, the textual practice of the Meditations still retains characteristics of ancient asceticism, though its modern legacy has obscured this dimension.

The Meditations as a Technique of Spiritual Exercise

This section reinterprets Descartes' Meditations within Foucault's framework of "care of the self," pointing out that the "cogito" is not a substance but a self-technique, and that the entire text aims to transform the subject's mode of being through spiritual exercise in order to access truth. The author emphasizes that Foucault's problematizing framework asks: can modern readers, through reading the Meditations, transform their own mode of being and way of accessing truth? The modern Cartesian subject is accustomed to treating the text as an inert object, employing an objective, detached, technical attitude to perform logical, dissecting interpretations; whereas reading the text as spiritual exercise can free one from disciplinary constraints, recognize the active power of the text, and shape subjectivity as a practitioner of the cogito through reinterpretation. This Rortyan pragmatist ethics of reading advocates that reading serves the expansion and renewal of "us," obtaining a new self through the self-labor of reading. Restoring the ancient ascetic dimension of the Meditations can, without destroying the cogito, loosen the rigid position of the modern subject and open the door to new modes of subject formation—this is precisely the true meaning of Foucault's "Cartesian Meditations" against Derrida's criticism.