Immanence, in an ontological context, is the thesis that the cause or ground of nature and all of its diverse phenomena is (in some sense) internal to nature. Spinoza's work is of interest in this context because, through his innovative use of the substance/mode distinction, it provides the theoretical articulation of a nontranscendent explanatory relation between the multiplicity of natural phenomena and their ‘immanent’ – that is, internal – cause. In her book, Beth Lord argues, however, that by examining the theme of ‘immanence’ in the work of Kant and Spinoza – as reflected in the interpretations of F. H. Jacobi, J. G. Herder, Salomon Maimon, and Gilles Deleuze – ‘a line of critical self-reflection concerning transcendental philosophy itself’ is subsequently made explicit (p. 1).

In her Introduction, Lord provides some historical context and a helpful overview of Spinoza's ontology. In Spinoza's monistic ontology there is exactly one infinite substance, while the multitude of finite things in nature – mere ontological extensions of this one substance – is characterized as its numerous modes. In chapter 1, Lord discusses Jacobi's reading of Spinoza and locates his use of the latter's key substance/mode distinction within the context of Kant's transcendental idealism. In this Kant-internal framework, Jacobi's interest in a Spinozistic ontology appears to derive mainly from his interest in closing an epistemic gap opened by Kant's phenomena/noumena distinction, thereby rescuing Kant's system from an alleged ‘nihilism’. In chapter 2, Lord reports on the (largely negative) historical reactions to Spinoza's dogmatism – according to which atheism and fatalism are the unavoidable implications of Spinoza's ontological monism – and she further elaborates on how Spinoza's ontology was viewed as a threat to moral freedom.

In chapters 3 and 4, the predominating issue is how to adequately explain the phenomenon of natural organisms (natural teleology). In chapter 3, Lord discusses Herder's vitalist reading of Spinoza – a reading which is intended to make Spinoza's thought compatible with Christian theism and moral freedom. Under Herder's reading, Spinoza's one infinite substance is retooled as an ‘organic force’ – the efficient cause of nature and all of its diversity. Here Lord discusses the issue whether a reconceptualization of the one infinite substance both as a ‘field of forces’ and as the subject of the traditional magazine of divine attributes (for example, intelligence, wisdom, intention) is conceptually coherent.

In chapter 4, Lord discusses Herder's ‘teleological naturalism’ – a view that incorporates the vitalist reading of Spinoza developed in chapter 3 – and shows (convincingly, I think) that Kant believed Spinoza's ontology, whether under a revisionist interpretation such as Herder's or under a more historically accurate reading such as Jacobi's, to be both theoretically inadequate to explain natural teleology and incompatible with the physico-teleology developed in the Critique of the Power of Judgment.

Whereas in chapters 1–4 the theme of immanence is pursued largely in an ontological context, in chapters 5–7 – where the book really picks up steam – this theme is pursued in a more epistemological context. In chapter 5, Lord presents her reconstruction of Maimon's work on Kant. Under Lord's reading, ‘Maimon's project is an attempt to push transcendental philosophy further, until it discovers the rationalist structure within which alone Kantianism is credible’ (p. 108). Maimon's aim is to rescue Kant's transcendental idealism from certain problems through the use of Spinozism. The resulting doctrine – ‘Spinozistic idealism’ – maps Spinoza's key distinction between a substance and its modes over transcendental idealism's distinction between appearance and reality. Under this mapping, reality is the one substance – the infinite mind – while appearance is equivalent to its many finite modes. The one substance is real; the modes are ideal (here meaning ‘mental’).

According to Lord, Maimon's interest in Spinoza's work is largely motivated by a concern to defend Kant against sceptical worries directed at the general structure of Kant's transcendental deduction.

According to Lord, Maimon thinks that Kant needs to defend (2) from sceptical worries. The problem is that Kant never shows that experience is in fact a series of necessarily connected representations; therefore, Kant is not entitled to infer a model of the mind's deep-structure according to which the (putative) datum of norm-governed experience is to be underwritten by a shortlist of a priori transcendental conditions (the categories of the understanding). In other words, unless we can shore up sceptical doubts about (2), we are not inferentially entitled to (3).

How should we link this problem to Maimon's Kant-internal use of Spinoza? What is to be gained theoretically by using Spinozistic innovations in a Kant-internal framework? Specifically, what problem within Kant's representational theory of mind could stand to gain anything by importing Spinoza-like elements into it? Before we can get a better grip on how to answer that question, we need to have a better grasp of what the problem is.

The source of the trouble, according to Lord, appears to be the formal (formalist) apparatus of Kant's epistemology. According to Lord, Maimon's criticism of Kant is that ‘there remains a gulf between sense intuitions, which are disparate and contingent, and pure concepts of the understanding, which are universal and necessary’ (p. 113). Kant's modular model of the mind is one under which there are multiple ‘faculties’ – for example, sensibility and understanding – that function concurrently in empirical cognition. Kant distinguishes between concepts and intuitions; concepts are the business of the understanding; intuitions – or, to borrow Jay Rosenberg's term, intuiteds Footnote 1 – are the business of sensibility. And since the relation between concept and intuited is that of the universal to the particular, the implication is that sensibility's job is to perform a specificatory function vis-à-vis the understanding's general concepts. In the context of empirical cognition the understanding provides a set of a priori representational norms – the categories – while sensibility provides the perceptually given exemplars or instances of those general norms.

A consistent theme running through chapters 4–7, but centrally in Lord's discussions of Maimon and Deleuze, is the problem of discursive ‘contingency’ – that is, the underdetermination that marks (or afflicts) the relation between concepts and their instances. In spite of its apparently central importance to Maimon and Deleuze's readings of Kant, the problem of discursive contingency is not made explicit in Lord's discussion. The idea of conceptual determination seems to contain two operative notions – first, the idea of necessity and, second, the idea of specification. Conceptual specification entails the possibility of multiple instantiation, which, in turn, requires that the members of a concept's extension be marked by two characteristics: ‘homogeneity’ and ‘heterogeneity’. All members of a concept's extension must be homogeneous in that they must be relevantly similar to – or, ‘the same as’ – the concept of which they are instances. But for a concept to be multiply instantiable, its members must also be sufficiently distinct – that is, heterogeneous – from each other if they are to count as different instances of the same concept.

Now those properties in virtue of which two or more members of a concept's extension are distinct from each other cannot be homogeneous with (or stand in a sameness relation to) the concept of which they are instances. If this were the case, a concept would evidently have to forfeit its generality. For if a concept contained (in its intension) the heterogeneous characteristics in virtue of which one member, x, is distinct from another, y, then its sameness relation to x would preclude it from also standing in a sameness relation to y. It may be for this reason that in the Jäsche Logic Kant describes the relation between a concept's intension and extension as an inverse relation; the broader a concept's extension, the less is included in its intension; alternately, the more inclusive a concept's intension, the narrower is its extension.Footnote 2

Conceptual specification would therefore appear to be at odds with conceptual determination. If a concept can determine, in the sense of necessitate, only what can legitimately be analytically specified from it, then it would appear that sensible objects cannot be conceptually determined. Invariably it is going to be the case that the members of a concept's extension are going to possess subsets of (heterogeneous) features that do not stand in a sameness relation to the concept of which they are (putative) instances. So these features will not be conceptually determined. And to the extent that a thing cannot be ‘what it is’ without this subset of ‘alien’ features, its possibility and existence will (to that extent) fail to be underwritten by its concept. Since every intuited, as a singular thing, must have heterogeneous properties and since presumably at least some of these properties will contribute nontrivially to what it is, the inevitable mismatch between concept and instance would appear to pose a serious problem for Kant's epistemology.

Conceptual underdetermination poses a legitimate threat to Kant's project, since in the framework of transcendental idealism it is a set of a priori hypergeneral concepts that are supposed to determine our experience of objects. What (in Maimon's view) does Kantianism stand to gain from Spinozistic idealism? Answer: a theory of immanence. In the context of dogmatic metaphysics (as in Herder's reading of Spinoza), a theory of immanence asserts that the cause or ground of nature is internal to nature – a Spinozistic thesis historically construed as pantheism. Under Spinoza's substance/mode distinction, finite minds, being merely modes, are ontological extensions of one infinite mind. In an epistemological context, a theory of immanence seems to be a theory of the relation between determinable and determinate content; it co-opts Spinoza's substance/mode distinction in order to explain (or, at any rate, explicate) the determinate content of empirical cognition as the expression of an infinite understanding's (indeterminate) ideas.

According to Lord, Maimon thinks Kantianism can survive only within the framework of rationalism (p. 123). What this seems to mean is that Maimon's model of the understanding comes equipped with ‘ideas’, ones that contain (what Maimon calls) ‘differentials’. Lord's detailed discussion of Maimon's notion of differentials cannot be pursued here. Suffice it to say, Maimon's differentials appear to have both Leibnizian and Kantian features. Like Leibniz's ‘complete concept of a thing’, differentials contain all there is to know about a given thing – both matter-of-factual and counterfactual properties. Maimon's ‘ideas of the understanding’ are Kantian in that, functionally speaking, the epistemic role they play – in providing a rule for representation – is similar to that of the categories within the framework of transcendental psychology. However, Maimon's ideas (differentials) are not at all hyperabstract content-bearing entities in the way the pure categories of the understanding are. Rather a differential appears to be a fixed yet intensionally rich content-bearer – a rule that determines all possible (sensible) predicates of a thing, both relational and nonrelational.

Under a Kantian model of empirical cognition, human representational systems bring to bear certain formal cognitive structures on ‘the deliverances of the senses’. Under this model, sensible content – the perceptually given – is received from some external source, whereas certain a priori formal structures, ones that are constitutive of the human mind, are imposed on those given materials. By contrast, the key Spinozistic innovation of Maimon's is this: Instead of the understanding bringing merely a formal cognitive structure to bear on perceptually given materials, the (finite) understanding, being a mode of the infinite mind, actually generates the ‘matter’ of sensation – that is, the determinacy of empirical cognition – from its ideas (or differentials). The philosophical payoff of using Spinoza to revise Kant is apparently the prospect of closing the yawning gap between the certain formal cognitive structures (as represented by the categories of the understanding) and the actual sensible content of empirical intuition.

In chapter 6, Lord pursues the theme of immanence in the work of Gilles Deleuze. Like Maimon, Deleuze is concerned to close the discursive gap between concept and instance, category and sensible intuition, thought and being. Lord reads Deleuze's ‘transcendental empiricism’ as a Maimonian response to Kant's transcendental idealism. Deleuze co-opts Maimon's criticism of (what might be termed) Kant's epistemological formalism.

Like Maimon, Deleuze also thinks that Kant's transcendental idealism is largely responsible for the yawning gap between concept and instance (category and intuited), thought and being. Kant cannot account for the ‘depth’ of appearances because transcendental idealism captures only the conditions of possible experience, not the conditions of real experience. ‘Kant cannot account for the being of the sensible’ (p. 131). So a transcendental empiricism is presumably a theory that states the necessary and sufficient conditions, not for the formal structures characterizing empirical cognition but rather for the determinate content of discursive representation – that dimension of empirical cognition that, under transcendental idealism, is outsourced to our perceptual capacities (sensibility).

According to Deleuze, Kant's approach is ‘too empirical’. Under an empiricist model of cognition, data are passively received from a source that is external to the mind. Within the theoretical framework of Kant's epistemological formalism, only an ‘external’ mode of conceptual determination is available, one whereby certain formal cognitive structures are used as an explanatory apparatus to ground the identity and individuation of sensible objects. But neither a set of hypergeneral categorial concepts (for example, substance, cause, etc.) nor the purely formal properties of geometry (for example, a bounded region of three-dimensional space) nor a general metaphysics of extended matter is sufficient to determine a thing's sortal properties – that is, the kind of thing it is. And since we encounter a vast multitude of diverse kinds of thing in empirical cognition, it would seem Kant's formalism, whether discursive or intuitional, is explanatorily inadequate. What is apparently needed, then, is a theory of ‘immanent virtual multiplicity’.

Deleuze's solution – transcendental empiricism – must therefore offer an internal (not exclusively external) means of object-determination. Here it appears Deleuze borrows heavily from Maimon in that he co-opts Maimonian ideas or ‘differentials’, which, functionally speaking, perform much the same theoretical role for Deleuze as they do for Maimon – namely, that of closing the discursive gap; however, whereas for Maimon differentials are conceived as fixed rules for the representation (or actualization) of real objects, Deleuze conceives ideas in less static terms, namely, as ‘the internally determining conditions that produce intensive real objects that differ in kind’ (p. 137).

According to Deleuze, transcendental empiricism qualifies as a ‘superior empiricism’ because, supposing it true, the mind would possess the internal resources needed to endow its cognitions with determinacy without having to receive data from a source external to it. However, the alleged superiority of Deleuze's transcendental empiricism requires an ancillary Spinoza-like metaphysics – ‘an alternative model of immanent self-differentiation’ (p. 153). Under this model, one that Deleuze claims is implicit in Kant's theory of the transcendental subject, Being objectifies itself for the sake of providing – through its expressive activity – its own determinate intentional object. In doing so, Being creates the difference between thought and being and ‘in this difference lies its power – its power to immanently generate the real’ (p. 153).

In chapter 7, Lord pursues the theme of immanence in Kant's Opus Postumum, and argues that, while Kant's conception of ether performs a theoretical role similar to that of Maimon's ‘ideas of the understanding’ in that the former, like the latter, functions as a ‘material principle constitutive of experience’ (p. 159), the conceptual framework of Kant's transcendental idealism nevertheless remains non-Spinozistic in several important respects – one being that Kant upholds the ontological distinctions between God, self, and world.

Although I found her discussion of Deleuze to be (at times) impenetrably opaque, Lord does a convincing job of showing that a concern with immanence (although variously articulated) is indeed an identifiable and philosophically interesting theme in the work of Kant and Spinoza and their interpreters. Indeed, when reading Lord's book (especially chapters 4–6), one may link her historical discussions on the relation between thought and being to contemporary concerns in the philosophy of language over the theoretical feasibility of a formalist semantics.Footnote 3