Kant's Modal Metaphysics

Anglophone philosophers with even a passing knowledge of Kant are no doubt familiar with some of his most notable arguments and positions. His conception of the synthetic a priori, the ideality of space and time, and the connections between self-consciousness and the objectivity of representation are all well known. Even more so are Kant's negative arguments against various metaphysical views popular in his day. His critiques of a priori arguments such as the ontological argument and those concerning the nature of the soul earned him Mendelssohn's rueful moniker as the “all-crushing” (alles zermalmenden) Kant, and remain staples of philosophical discussion.Nicholas Stang, in his new book Kant's Modal Metaphysics, presents a reading of Kant's philosophy that emphasizes the enormous significance of Kant's conception of modality for his mature “critical” philosophy. If Stang's interpretation is correct, then Kant's modal metaphysics warrants much greater attention than it has historically received, with Kant's arguments concerning our knowledge of the grounds of metaphysical possibility deserving inclusion among the pantheon of his more famous arguments mentioned above.The book consists of two roughly equal parts. The first discusses Kant's precritical position and primarily focuses on his comparatively neglected work The Only Possible Ground of Proof for a Demonstration of the Existence of God (or “Beweisgrund” for short) of 1763. The second turns to Kant's critical modal metaphysics, from the 1781 Critique of Pure Reason up to the 1790 Critique of Judgment. As one can no doubt tell from the sweep of the texts discussed, Stang's project is incredibly ambitious. It is also enormously rich. Even if one comes away unconvinced by the details of some of Stang's arguments, the overall case that he makes for the centrality of Kant's modal metaphysics to his overall philosophical outlook is both impressive and extremely fruitful. However, precisely due to the richness of the book's discussion I shall discuss only a few of its major arguments (and quite briefly at that), offering a few critical remarks along the way. In particular, I focus on Stang's interpretation of Kant's precritical development of an anti-“logicist” theory of modality, as well as Stang's conception of the unity of Kant's precritical modal theory with the critical theory of the 1780s and 1790s.The first part of the book is largely concerned with laying out and evaluating a dispute between, on the one hand, the precritical Kant and, on the other, advocates of a position Stang dubs “Logicism.” The issues at the heart of Kant's criticism of logicism concern the nature of possibility and necessity, and how we can come to know that something is “really”—that is, metaphysically—possible.Real or metaphysical possibility concerns the being or existence of the thing or event in question. For example, in asking whether an extended thinking substance is really possible, we are asking whether a being could exist that instantiates properties of being extended and of thinking.How can we represent and come to know answers to questions about such possibilities? According to the logicist, our capacity to represent and ultimately know answers to such questions hinges on our (conceptual or discursive) ability to represent propositions that do not entail contradictions. Stang provides plausible evidence for construing significant figures in the German philosophical tradition immediately prior to Kant as logicists, including Leibniz, Wolff, and Baumgarten. According to these figures metaphysical possibility (and necessity) is taken to be identical with certain kinds of logical relationships (hence the “logicist” moniker).Stang also introduces a position he calls “Ontotheism,” which is the view that God's existence is grounded in his essence (27). Stang takes any logicist who agrees that God exists necessarily to be thereby committed to ontotheism. Why are they so committed? Since logicism holds that all necessities are logical necessities, and given the necessity of God's existence, this necessity must be understood in terms of the logical relation that holds between the concept and the concept . The former entails the latter because is taken by the logicist to be a constituent of (or “contained in”) the concept .Kant clearly rejects ontotheism as early as his Nova Dilucidatio of 1755 (see Ak. 1:394). The root of Kant's criticism of ontotheism is his famous claim that existence is not a “real” predicate. Stang argues (in sec. 1.5) that logicism, via ontotheism, is committed to the opposing position. Hence, in claiming that existence is not a real predicate, and given his commitment to the position that God exists necessarily, Kant must reject the logicism of Leibniz, Wolff, and their followers.What does it mean to say that existence is not a real predicate? Stang distinguishes between two positions—possibilism and actualism. According to possibilism, possibly, some objects do not exist. Thus to say, with possibilism, that there could be possible but nonexistent objects is to say that is a normal or “real” predicate. With respect to real predicates we can say, of a class of objects, those to which the predicate applies and those to which it does not. So, if possibilism is correct then we can apply in the same manner as any real predicate. We can use it to say, of all the objects there are, that some of those objects exist. To deny that the concept or predicate functions in this way is thus to deny possibilism and assert what Stang calls “actualism,” or the claim that, necessarily, all objects exist.In more contemporary terms, Stang understands Kant's claim that existence is not a real predicate to mean that (i) “exists” is a quantifier, and (ii) that this quantifier is unrestricted in its scope. The first claim, that “exists,” or better, “there is” (41), is a quantifier, has been argued for by a number of others (e.g., Bennett 1974, 228–32; Van Cleve 1999, 189; for an opposing view, see, e.g., Rosefeldt 2008). It is the second claim, concerning quantifier scope, where Stang makes his central contribution to the debate. He takes the main disagreement between Kant and the ontotheist to be whether or not the existence quantifier is restricted (38–39). Ontotheism, insofar as it is committed to possibilism, says that the quantifer is restricted, that is, to the subset of objects that exist, while Stang's Kant says that it is not restricted, applying to all the objects that there are.So, if the ontotheist is committed to possibilism, what follows? Well, if Kant is right that existence is not a real predicate, then it is wrong to say that there are objects (in the quantificational sense) that do not exist, so possibilism is false, and so is ontotheism. Moreover, since the logicist is committed to ontotheism by virtue of their view of the necessary existence of God, the logicist position is also in jeopardy.So, is the ontotheist committed to possibilism? This is less clear. For one, it may be questionable to restate the logicist ontotheist position using modal operators, since part of the point of being a logicist is that all alethic modal notions are equivalent to logical ones. The logicist might say that it is a logical truth that God exists, and that it is logically coherent to deny the existence of all other beings. If logicists thus reject any introduction of modal operators it will be correspondingly difficult to show that they are, qua ontotheists, committed to possibilism.1 Stang somewhat encourages this problem by emphasizing that “the logicists need not agree with Kant about what logic is” (76). But if this is correct then perhaps the logicist/ontotheist can reject other logical principles, such as those concerning the introduction or elimination of the necessitation operator (or simply deny its introduction entirely). Stang himself thinks a sufficiently sophisticated ontotheist can deny Kant's arguments (though there are other routes to denying logicism, as Stang discusses in chap. 3). The question is whether the ontotheist can deny them at an even earlier juncture—that is, in the commitment to possibilism itself.Let's turn now to Stang's position regarding the unity of Kant's modal views from the precritical to the critical period. Allowing that modal considerations may only be one of a host of issues that push Kant to the doctrines constituting the critical philosophy (161), Stang nevertheless maintains that through the changes of Kant's view from the 1760s to the 1790s, there is a remarkable consistency or unity in his underlying conception of modality. This unity stems from Kant's purported acceptance, from the 1763 Beweisgrund all the way through the critical period, that “the most rationally satisfactory explanation of real possibility” (296) is the conception of God as the ground of all real possibility (GARP). What changes in the critical period, among other things, is Kant's evaluation of the epistemic status of this “rationally satisfying explanation.” Specifically, Stang's critical Kant denies that we can have knowledge that a divine GARP exists. Instead, we must settle for rational belief (what Stang calls “necessary theoretical belief,” which is a species of “doctrinal belief” [A825–26/B853–54; cf. Chignell 2007]). Stang supports this position most convincingly in his commentary on Kant's discussion of the ens realissimum in the opening of the Transcendental Ideal of the Critique of Pure Reason. As Stang notes, the argument of the Beweisgrund has been here “transposed from a dogmatic metaphysical to a critical-subjective key” (294) such that it is now presented as the only way of satisfying our faculty of reason's regressive (dialectical) demand for the unconditioned, and in this case, for the explanation of why anything is really (noumenally) possible at all (327).Stang goes on to defend an interpretation of Kant's 1790 view that avoids what otherwise looks like a commitment to an inconsistent tetrad of claims concerning God's intuitive intellect and properties of noumena that would be cognized by this intellect (298).Stang argues that the best means of resolving this “modal antinomy” is to find “noumenal correlates” (312) of our (unschematized) modal categories—specifically, and —in God's differential cognition of objects as depending, respectively, either on his nature or on his will. On this view is used to think about God and everything posited by God's will, and is used to think about everything God has the power to posit (327). Stang also uses this view to resolve a putative “tension” (146) of the Beweisgrund between Kant's denial that God grounds possibility through his powers (because his powers are among the possibilities that need grounds), and—on Stang's interpretation—the fact that Kant “implicitly” thinks of God as grounding possibility causally through his powers.This is, to be sure, a neat way of tying together various strands of Kant's precritical and critical views. If cogent, it would further strengthen Stang's claim to have found a central strand of Kant's thinking that both motivates and, in certain ways, persists through the critical turn. But the connection Stang makes requires insisting that it is plausible to represent the noumenal correlates of modality as grounded on God's powers of willing and positing. But it's not obvious that one is representing anything at all when attempting to represent the existence of a power that is not to be understood in modal terms. Why? Because the concept of a power (i.e., the representational content of the concept ) seemingly includes or partially consists in the representation of something as possible (e.g., to represent the power of x to produce F one must represent x as possibly instantiating/producing F). Thus, the content of cannot explain that of because it presupposes the latter. If that is correct then, pace Stang, there is a “barrier to thinking that God grounds various noumena and their properties” (327), including noumenal correlates of the modal categories, via his powers—that is, the very unthinkability or unintelligibility of claiming that the concept of power could ground or explain the modal category of possibility.This issue also threatens Stang's view that the critical Kant maintains a rational belief in God as the ground of all real possibility, at least in the powers manner that Stang suggests. For such a belief to have the status of a “necessary theoretical belief” its object must be logically possible, and must not be knowably really impossible (287). But our inability to represent a power that is the ground of possibility suggests that it is logically impossible that God's powers ground (by providing noumenal correlates of) our conception of the possible and the actual. Hence it cannot be rational to believe in such a ground of real possibility, as least as Stang is conceiving of it.These worries aside, the rigor, depth, and breadth of the book is truly impressive. It is required reading for anyone interested in Kant on modality, or more broadly, in the content and defensibility of Kant's metaphysical and epistemological views, both prior to and throughout the critical period

Epistemology · Metaphysics · Objectivity (philosophy) · Classical Philosophy and Thought · Philosophical Ethics and Theory · Philosophy · Philosophy and Historical Thought

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