Kant’s pre-Critical period writings, roughly, from 1747 to 1770, have received much less attention from philosophers and historians then they deserve, an oversight that is perhaps due to the mistaken belief that these early works simply parrot the Leibniz-Wolff school’s doctrines. Matthew Rukgaber’s book attempts to dispel these erroneous impressions through a unique interpretation of the role of space and time in the pre-Critical period, as well as by offering a highly unorthodox reconstruction of the motivation behind Kant’s Critical turn c.1768–70. The book reveals a thorough knowledge of the primary and secondary literature, and Rukgaber goes to great lengths to justify his interpretation against the standard commentary. As will be argued below, however, the textual evidence does not support his central claims, nor are some of the conceptual categories that he applies adequate to the task. Nevertheless, the book is engaging and thought-provoking, and some of the arguments advance the commentary in a positive direction. For instance, chapter 4 makes a sound case against those commentators who claim that Dreams of a Spirit-Seer thoroughly repudiates the earlier monadological system.
After an introductory chapter, the central theme in chapter 2 is the rejection of a relational interpretation of Kant’s pre-Critical conception of space for a ‘supersubstantivalist’ reading, using Sklar’s terminology (Sklar Reference Sklar1974: 221). Rukgaber contends that ‘Kant’s view of space is akin to what Sklar calls a “variant on the substantivalist position”, in which “all there is is spacetime”, which means that the “ordinary material contents of the world should be viewed as ‘pieces’ of spacetime itself” (Sklar Reference Sklar1974, p. 166)’ (p. 22, also p. 164). The supersubstantivalist view is associated with several older spatial ontologies in Sklar’s work, such as that of Plato’s Timaeus and Descartes’ plenum, but its ‘fullest development’ is linked to Wheeler’s geometrodynamics (Sklar Reference Sklar1974: 222), an early attempt to unify gravity with the other fundamental forces, and which resembles contemporary quantum gravity hypotheses. Geometrodynamics is constructed from the metric of General Relativity, and hence spatial extension and geometry are presumed from the outset (and this also holds for Plato’s Receptacle, Descartes’ plenum and Newton’s ‘determined quantities of extension’ hypothesis in De gravitatione). Kant’s view in the pre-Critical period, by contrast, starts with an ontology of non-spatial, non-extended monads from which matter and space supervene or emerge (via the force-based monadic interconnections; cf. PhyM, 1: 481–2).
Thus, supersubstantivalism is not only an incorrect classification, but it would seem to represent the opposite strategy in relation to Kant’s approach. The correct quantum gravity correlate of Kant’s monadology would be those hypotheses, such as causal set theory, that envision the metric of General Relativity as emerging from the causal interconnections of non-spacetime elements. Furthermore, Sklar defines relationism as rejecting the view that space and spacetime are ‘entities existing in their own right’ (Reference Sklar1974: 167), a rejection that more accurately corresponds to Kant’s conception since space is ontologically dependent on monadic force interconnections: for example, ‘there would be no space and no extension if substances had no force to act external to themselves. For without this force there is no connection, without connection, no order, and, finally, without order, no space’ (LF, 1: 23). Another difficulty for the non-relationist interpretation is that Kant embraces relationism in his pre-Critical ‘New Doctrine of Motion and Rest’ (1758), a fact that prompts Rukgaber to comment that the rejection of absolute space in that tract is ‘compatible with an ontological commitment to substantive space in some sense’ (p. 113) – yet, as just noted, it is more compatible with relationism in Sklar’s (and most other people’s) sense of the substantival/relational distinction. Overall, it is difficult to gauge the exact spatial ontology that Rukgaber attributes to Kant, for there would seem to be inconsistencies and textual inaccuracies in his analysis: for example, he argues that ‘Force is not prior to space. It is space’ (p. 46, n. 15), even though, as in the quote above, force is listed as prior to space in his ontological taxonomy (i.e., force, connection, order, space). Later, Rukgaber states that ‘[s]pace is the product of the co-existence of metaphysical substances’ (p. 52, n. 80), which not only sounds relational, but also seems to have demoted force in favour of coexistence.
The causal relationship between Kant’s monads and matter/space is the central topic of chapter 3, and Rukgaber correctly rebuffs the idea that Kant’s monads are situated in space (or so it appears, since his inaccurate handling of the ubiety categories raises doubts): ‘[t]he monad is only physical in its external presence and cannot be thought of as a point in space’ (p. 61). Rukgaber employs the scholastic concept of definitive ubiety to characterize his interpretation of the monad–matter relationship (see, for instance, p. 90), but he overlooks one of the central aspects of this hypothesis, which, as Grant explains, is ‘characterized by the assumption that a spiritual substance could fill not only the whole of the place that delimited it but the whole of that spiritual substance, for example, an angel or soul, was in every part of its place or ubi definitivum’ (Grant Reference Grant1981: 343, n. 67). By the seventeenth century, definitive ubiety was synonymous with the ‘whole in every part’ doctrine, or ‘holenmerism’ (as More dubbed it), which regards the substance of immaterial beings as actually situated wholly in each part/point of matter/space. But Kant does not regard the monad’s substance per se as present in space, and Rukgaber seems to agree (as noted above, p. 61, and p. 103, n. 50), so definitive ubiety is not the correct classification for the monad’s relationship to matter/space. In Dreams of a Spirit-Seer, Kant does employ the ‘whole in every part’ terminology, but that description pertains to the relationship between an immaterial being and a pre-existing material body, such as a soul or spirit inhabiting a human body, which is a quite different case than the relationship between a monad and the matter that directly emerges from it (i.e. Kant holds that a spirit occupies a space through activity without filling it through impenetrability, whereas a monad both occupies and fills a space; DSS, 2: 321–4). If one is forced to pick an ubiety option, then the correct form is much closer to Leibniz’s idiosyncratic conception of repletive ubiety (and leaving aside the infinite versus finite being distinction). In the ‘Physical Monadology’ (PhyM, 1: 481), Kant defends his view that a monad’s inner determinations are not in space by offering an analogy with God’s ‘act of preservation’ of the material world, an example that exactly matches Leibniz’s definition of repletive ubiety in the New Essays (Leibniz Reference Leibniz, Remnant and Bennett1996: 222). Not only does Leibniz insist that God preserves the world without being present in space (Leibniz Reference Leibniz and Loemker1969: 683, 710), but the causal relationship between Kant’s monads and the matter that emerges from them is also quite similar to God’s causal act of continuously preserving the world (whereas definitive ubiety is restricted to souls/spirits occupying bodies that they did not causally bring into being). Likewise, Kant’s description of God’s role in upholding the inter-monadic connections (the schema of the divine understanding; cf. NE, 1: 413–14) would qualify as repletive ubiety under Leibniz’s interpretation, since it is an act of preservation; thus, it is incorrect to claim, as Rukgaber does, that Kant’s ‘God has no ubiety’ (p. 90).
By far, the most problematic portion of the book resides in the last three chapters, which attempt to provide a non-psychological or non-cognitive, externalist reading of Kant’s ‘Directions in Space’ (1768) and Inaugural Dissertation (1770), the two works which anticipate the turn to the Critical period, although Rukgaber seems to extend this interpretation to the Critical period as well. In what follows, I will mainly confine the discussion to the incongruent counterparts argument in chapters 5 and 7. In brief, Kant’s 1768 piece uses the example of handedness (an object whose mirror image cannot be superimposed on it, such as left- or right-hand) to argue for absolute space, which Rukgaber links to his supersubstantivalist view and a ‘qualitative monadic property of handedness’, concluding that ‘[m]atter has certain spatial properties because it emerges from space itself’ (p. 164). But this interpretation conflates space and matter (the former is infinitely divisible, the latter is not), and it gets the ontological dependency relationship backwards: ‘space … is entirely free from substantiality and … is the appearance of the external relations of unitary monads’ (PhyM, 1: 479). Kant states that the ‘inner ground’ upon which the handedness difference rests does not depend on ‘the manner in which the parts of the body are combined with each other’ (FGDS, 2: 383), hence, since ‘bodies consist of monads’ (PhyM, 1: 477), the constitutive relationship among a body’s monads cannot account for handedness. Turning to individual monads, the ‘sphere of activity’ (external determination) is symmetrical, since it is a sphere, and thus it cannot be the basis of handedness either (whereas the internal determinations are excluded since they are not in space). So, without a foundation at the monadic or body levels, what then accounts for handedness? Kant’s famous answer in ‘Directions in Space’ – a passage which is not mentioned in Rukgaber’s book – foreshadows the later Critical period: ‘absolute space is not an object of outer sensation; it is rather a fundamental concept which first of all makes possible all such outer sensation’ (FGDS, 2: 383). This idealist conception of space, where it is described as a ‘unity’ and compared to the absolute space of the ‘geometers’ (FGDS, 2: 378), is retained in the Inaugural Dissertation, but it is now wielded against both the absolutist and relationist: space is ‘subjective and ideal; it issues from the nature of the mind in accordance with a stable law as a scheme, so to speak, for coordinating everything which is sensed externally’ (ID, 2: 403). Interpreting these types of passages as promoting a non-cognitive, direct realist epistemology and metaphysics (e.g., p. 253, n. 29) is, to say the least, extremely difficult, if not impossible. For example, Rukgaber translates Kant’s claim that there is ‘a certain law, which is inherent in the mind and by means of which it co-ordinates for itself that which is sensed’ (ID, 2: 393) as simply pertaining to ‘our own position and perspective in the world and our directional possibilities’, but it ‘does not mean that we drape spatial and temporal properties on naked data’ (p. 245). This externalist rendition drastically changes the intended meaning and purpose of the original, and hence Rukgaber’s contention that ‘the externalist view is able to accommodate everything that appears in the internalist idiom’ (p. 245) is refuted by his own example.
In addition, the externalist reading is also open to the charge that it renders space empirical, and thereby undermines the necessity of the axioms of geometry: ‘if all the properties of space are merely borrowed by experience from outer relations, then there would only be a comparative universality to be found in the axioms of geometry, a universality … [that] extends no further than observation’ (ID, 2: 404). The necessity of geometry is, in fact, one of the key motivations that Kant cites for his new subjectivist approach, a factor that is completely eliminated under an externalist construal. Since ‘nothing at all can be given to the senses unless it conforms with the fundamental axioms of space and its corollaries (as geometry teaches), whatever can be given to the senses will necessarily accord with these axioms even though their principle is only subjective’ (ID, 2: 404). In essence, the three-dimensional Euclidean space of the geometers, which the earlier Newtonian absolutists conceive in externalist fashion as some sort of entity, has been internalized as a cognitive feature by Kant, a manoeuvre that secures the axioms of geometry in the same way as the absolutists but absent their ontology. Consequently, while Rukgaber’s book presents an interesting exercise, his externalist exegesis simply cannot be superimposed on the original texts – an interpretational ‘incongruent counterpart’ to Kant, as it were, whose misdirected orientation can only be determined with respect to the unity of the space of Kantian scholarship.
