In Squaring the Circle in Descartes’ Meditations, Stephen Wagner aims to show that Descartes’ project in the Meditations is best understood as a ‘strong validation of reason’ i.e., as proving in a non-circular way that human reason is a reliable, truth-conducive faculty. For such an enterprise to qualify as a ‘strong’ validation, Wagner contends, skeptical doubt must be given its strongest force. The most stringent doubt available in the Meditations is the deceiving God. To rule out the possibility that an omnipotent God created humans so that their best functioning cognitive faculties provide misleading information about what the world is like, Descartes must prove that a non-deceiving God exists. Furthermore, only a non-circular proof will count as a ‘validation.’ Wagner spells out the requirements of non-circularity as involving a proof for God’s existence that is not deductive, does not simply achieve a clear and distinct perception of God’s existence, and proceeds on the basis of perceptions that remain true even when the reasons underlying them are not attended to any longer by the meditator.

In opposition to most commentators^{Footnote 1} who agree that the strong validation project is absurd, impossible or both, Wagner sees it as realizable since pushing doubts to their extreme contains the very key to their resolution. According to Wagner, the linchpin of this strong validation of reason is the meditator’s Neo-Platonic and Augustine-inspired experience of participation in God’s thinking. Wagner purports to answer all the above-mentioned charges of circularity: God’s existence, we are told, is, in fact, proven experientially rather than deductively or by means of clearly and distinctly perceiving His existence. To achieve the experience of participation in God, Descartes instructs his readers to simultaneously attend to an idea of God as an infinite being as well as to a clear and distinct idea of God as perfect. For Descartes, Wagner claims, this experience is different only in degree, not kind, from the beatific vision of the afterlife.

Before turning to a close reading of the Meditations, Wagner provides an explanation of Descartes’ silence regarding this “experiential method of demonstration” (38). Descartes would not have explicitly mentioned his ‘experiential method’ because the Meditations follow an analytic method: the reader is expected to give his full attention to a preset sequence of steps thus discovering on his own many ‘transparently clear’ aspects deliberately omitted by Descartes (25). Moreover, the theological climate of the day determined Descartes to slant by omission many of his published views. Wagner contends that the Meditations III experience of participation in God’s activity of knowing Himself would have been considered theologically suspect due to its Jansenist and Pelagian undertones. Holding that the careful meditator is able, on his own and unaided by supernatural grace, to become a participator in God’s activity would have been censored by Church authorities so, Wagner continues, Descartes chose to hint at it rather than state it openly.

In reconstructing the trajectory of the Meditations, Wagner identifies in each of the first five an iterated pattern composed of three stages: first, Descartes specifies an epistemic goal. Second, conceptual and logical groundwork is laid in order to provide the reader with the tools needed to achieve the proposed goal. Then, a transition passage explicitly states that remaining doubts still hinder the sought-after goal. Third and finally, a cognitive exercise which amplifies those doubts is set up. The reader diligently working through the exercise will be rewarded with an experience revealing the presence of a power affecting his will. From here, cognitive resources necessary for future epistemic progress can be extracted. Chapters 3 through 8 of this monograph detail this three-part structure of Meditations I-V. Let us briefly look at each of these chapters; Arabic numerals will be used to mark the three-part structure Wagner identifies in each meditation.

(1) The Meditation I meditator sets out to withhold assent from any former beliefs which relied on the existence of external objects. (2) Since the skeptical arguments brought in to impugn his cognitive faculties (senses, imagination and reason) end up undermining themselves, the meditator needs non-reason-based means for suspending assent. (3) By conjuring up the evil demon the meditator “will experience both his ability to bring about the image of the demon and the power moving his will to a posture of suspended assent. As a result, he will take these two components of his idea to be brought about by the causal power of his imagination” (72).

(1) The purpose of Meditation II is to discover the existence of the meditator’s mind. (2) That means showing that his mind “must have a non-physical nature, that he must be using a faculty that is not dependent on external objects and that he must be perceiving a single essence of thinking which underlies all his mind’s activities” (78–79). But the evil demon still casts doubt on all these reasonings. (3) In the wax investigation, after arriving at the clear and distinct idea of the wax as extended, “the meditator discovers his mind’s ability to generate clear and distinct perceptions. In these perceptions, he experiences a power that compels his assent” (40) and realizes that he exists as a thinking thing.

(1) In Meditation III, Descartes aims to prove the existence of a non-deceiving God. Wagner claims that the wax exercise discoveries supply concepts (e.g., objective and formal reality, the causal laws and material falsity) needed for Descartes’ first deductive demonstration of God’s existence. (2) “On the basis of Descartes’ causal principles and his claim that the idea of God contains more objective reality than the meditator’s mind can cause, the meditator can conclude that something other than his mind exists as the cause of that idea” (152). (3) The resolution of lingering doubts (e.g., the problem of circularity and the meditator’s knowledge of his existence) lies in “experiencing his own activity of clearly and distinctly perceiving God as deriving from and united with God’s infinite power,” as “a participation in God’s activity of knowing Himself” (156).

(1) Meditation IV will prove that everything we clearly and distinctly perceive is true and explain the nature of falsity (ATVII, 15; CSM II, 11). (2) The meditator discerns his will’s different reactions to clear and distinct versus confused and obscure perceptions: compelled assent as opposed to indifference. As a result, he learns that properly using his will means withholding assent from perceptions that are unclear and not distinct. (3) The validation of this normative claim rests on experiencing the range of his mind’s operations within the context of his experience of God’s power. Descartes recognizes that “God’s power is compelling his assent and is creating the reality corresponding to what he is perceiving. By participating in God’s creative activity, he can be certain that he is not being deceived. His experience guarantees that what he is perceiving is true” (206).

(1) The target of Meditation V is certainty about material objects. (2) By analogy with his ideas of mathematical ideas which divide into parent notions (e.g., triangle) and dependent properties whose power to compel assent derives from the former, Descartes realizes that God and His necessary existence can be deductively linked. Since clear and distinct ideas are just God’s activity of knowing truths and creating the objects that make them true, all clear and distinct ideas are contained within the clear and distinct idea of God. Cartesian science is just the process of extracting these ideas from the idea of God via an uninterrupted sequence of deductive steps. (3) “The stage three cognitive exercise will establish [that the more complete idea of God is necessarily true] by directing the meditator to perceive God in this way while experiencing His infinite, self-creative power” (214).

While attempting to square the Cartesian Circle, Wagner closes the circle of interpretations of the role of God in Descartes’ system. Wagner argues that participation in God’s activity represents Descartes’ theistic response to radical skepticism. Wagner’s position appears as the polar opposite of Hiram Caton’s ‘dissimulation thesis’ viz. theological garb, materialist content^{Footnote 2}. Tracing the arc between these two extremes are, to mention just a few alternatives, Nolan’s ‘plausible when properly contextualized’ reading of the Meditation III arguments for God’s existence^{Footnote 3} and Della Rocca who views Descartes as setting the stage for an epistemology without God^{Footnote 4}. Closer to Wagner’s account, Secada^{Footnote 5} and Koistinen^{Footnote 6} find a central place for the meditator’s being possessed by and thinking with God, respectively.

Squaring the Circle is a well-written, thorough and innovative interpretation of Descartes’ Meditations. This monograph encourages further study of the relation of Descartes’ thought to the work of his contemporaries. It will be of interest to students and researchers of early modern philosophy in general and of Descartes’ views in particular.