2. Kant and natural laws

Since its initial publication, Kant’s critical philosophy has resurfaced at several decisive moments in the history of philosophy of science. In the nineteenth and early twentieth centuries, several philosophers of science – including William Whewell, Ernst Cassirer, Arthur Lovejoy and Hans Reichenbach – discovered in Kant a way of articulating both the general conditions of scientific knowledge and the autonomy of particular domains of scientific research. Yet if John Stuart Mill’s victory over Whewell is anything to go by, or the ascendency of logical positivism over Neokantianism, it seems that Kant’s synthetic a priori has not aged well. In the mid-twentieth century, the unity of science hypothesis rejected Kant’s attempt to retain a place for modality (causation, dispositions, counterfactual conditionals, etc.) in nature,Footnote ¹ and in the late twentieth century the idea of universal natural laws once again came under fire.Footnote ² The negative view of lawfulness is reflected within Kant scholarship itself. Some scholars have argued that Kant’s derivation of the properties of matter in Metaphysical Foundations of Natural Science is irredeemably tied to Newtonianism (Heidegger Reference Heidegger, Barton and Deutsch1967: 126), while others have attacked the Second Analogy for the famed non-sequitur by which Kant seems to assume without argument that nature adheres to the schematized concept of causality (Bennett Reference Bennett1966: 229; Strawson Reference Strawson1966: 137).

It may come as a surprise, then, to note that work on Kant’s theory of science underwent something of a renaissance in the latter part of the twentieth century. The resurgence of interest was partly motivated by the pioneering work of Peter Plaass, Gerd Buchdahl, Robert Butts, Gordon Brittan and Philip Kitcher, who appealed to Kant’s philosophy in response to a renewed emphasis on lawfulness in philosophy of science. Plaass ([1965] Reference Plaass, Alfred and Maria1994) criticized the interpretation of Kant’s critical philosophy that prevailed in the early twentieth century, which called on contemporary discoveries in mathematics and physics to expose Kant’s supposedly outdated account of space and time as pure intuitions. Instead, he appealed to transcendental idealism to clarify the metaphysical foundations of contemporary physics, claiming that the application of mathematics to the objects of scientific inquiry could never be grounded on a reality independent from thought but must depend on the structure of objecthood anticipated by the understanding. Buchdahl (Reference Buchdahl1969) contended that the schematized categories of the understanding do not govern how natural objects behave, which would entail a problem of inference from general category to particular law. Rather, the schematized categories prescribe the logical relations of dependence between appearances and their conditions, enabling the natural scientist to seek real causal relations that possess a non-logical, nomic necessity.Footnote ³ It is not the understanding but reason that ‘injects’ necessity into candidate lawlike propositions by virtue of the position they come to hold in a system of lawlike statements (Buchdahl Reference Buchdahl1969: 508–9). Generalizations ‘accrue’ necessity if they consistently and interdependently find their place in the best system.Footnote ⁴ Buchdahl’s reading highlights the way in which reason produces guiding ideas, which, formulated as principles, instruct how candidate lawlike propositions should be judged. While the ideas of reason are not constitutive of laws, they provide epistemic justification for adopting a rule as a law.

As Plaass and Buchdahl sought to reanimate Kant’s philosophy of science, the question of lawfulness became a central issue in the philosophy of science. For David Lewis (Reference Lewis1973: 73), generalizations can be counted as natural laws if they are axioms in all the deductive systems with the best combination of simplicity and strength. Thus, there is nothing intrinsic about a certain property or power. Extrinsic matters fix the powers that bearers have. In contrast, David Armstrong (Reference Armstrong1983: 85) rejected the subjective character of the ideals that govern Lewisian systematization and argued instead that the laws of nature consist of non-logical or contingent necessitation relations between universals. According to Armstrong’s necessitarianism, lawfulness does not supervene on local matters of fact, nor does it depend on subjective requirements. It is a relation that holds between the universals in which the particular instances of those universals participate.

Both accounts have well-noted problems. Defenders of necessitarianism criticize the Lewisian view for conceding that laws, because they are grounded in subjective ideals (simplicity, strength and balance), are mind-dependent (Armstrong Reference Armstrong1983: 66–73). Others claim that the Lewisian view raises a direction of fit problem. If a law supervenes on the occurrence of some fact, then it does not explain the occurrence of the fact. Rather, the occurrence of the fact explains the law; the direction of explanation goes the wrong way (van Fraassen Reference van Fraassen1989: 40–64). Critics of Armstrong’s necessitarian view argue that it raises a problem of inference (van Fraassen Reference van Fraassen1989: 96). Because laws are not causes, for they do not appear in space and time, the necessitarian view does not explain how they necessitate the empirical goings-on of nature (Lewis Reference Lewis1983: 366).

In the midst of this debate, several philosophers of science appealed to Kant to clarify some of the ambiguities associated with the notion of ‘best system’. Earlier in the century, Frank Ramsey ([1928] Reference Ramsey and Mellor1978) considered the best system as a fully deductive system of things we know. A system is ‘best’ if it is simpler than alternative systems. For Lewis (Reference Lewis1986), the best system is a system of both particular and general truths, but not necessarily deductive. The best system thus has the pragmatically best trade-off between simplicity and informativeness. Yet neither the Ramseian nor the Lewisian principles can be justified objectively. In response, Philip Kitcher attempted to vindicate principles of systematicity by appealing to the indirect objective validity of reason’s principles in the Transcendental Dialectic (CPR, A665/B693).Footnote ⁵ Following Kant, Kitcher argues that the best system is the one that brings greatest unity and extension to the understanding, the latter of which is valid in regard to objects. Reason’s principles coordinate the activities of the understanding and share in the objective validity of the categories to the extent that they (reason’s principles) introduce empirical laws – non-trivial and non-logical propositions that fill in the cause-effect template anticipated by the schematized concept of causality – to the best system (Kitcher Reference Kitcher and Butts1986: 209).

Kitcher’s attempt to fuse Kant’s account of lawfulness with the Lewisian best-system view has gained significant attention over the years. Yet few commentators have been convinced. As an interpretation of Kant, it fails to connect the necessity accrued by reason’s systematicity with the necessity spontaneously determined by the understanding (Friedman Reference Friedman1992). As a revised Lewisian view, it fails to overcome the problem of fit, for systematic unity cannot explain how laws necessitate or govern spatio-temporal events in nature (Messina Reference Messina, Massimi and Breitenbach (eds)2017: 136; Engelhard Reference Engelhard2018: 30). Kant clearly states in the Dialectic that empirical inquiry merely ‘approximates’ the kind of universality that knowledge seeks (CPR, A647/B675). To address this problem, Michael Friedman (Reference Friedman1992: 163) emphasized the necessitarian dimensions found in Kant’s account of causation, claiming that laws, insofar as they ‘subsume such regularities under the a priori principle of causality, … are necessary – and even, in a sense, a priori’. Friedman’s account grants two classes of particular laws: the laws of mechanics, which are derived by applying the transcendental laws to the empirical concept of matter (MFNS, 4: 496; cf. P, §38), and mixed particular laws, which require content beyond the empirical concept of matter (MFNS, 4: 518; cf. CPR, A662–3/B690–1). Both classes of particular law are nomically necessary to the extent that the transcendental laws are ‘injected’ into them (Friedman Reference Friedman1992: 175), meaning that they govern how nature must behave.

Friedman’s necessitarian account helped to establish that pure and mixed particular laws, if they are to govern material objects, must be grounded in the categories. Yet his necessitarian reading comes with the caveat that the remainder of particular laws, which are not grounded in the categories, are not strictly laws. While this conclusion appeals to some, for it paints Kant as an empiricist about particular domains of science while maintaining necessitation as an ideal, it opens a problem of inference similar to that raised by van Fraassen against Armstrong. The understanding’s laws are not causes, for they do not appear in space and time and thus cannot act on spatio-temporal things (Engelhard Reference Engelhard2018: 28). On Friedman’s reading, there is no legitimate way to infer from the necessity of possible objects to the necessity of empirical goings-on (Massimi Reference Massimi, Massimi and Breitenbach2017: 150–1).

Given these problems, Kant scholars have found a new way of presenting the non-logical necessity of particular laws by engaging with the broader turn to causal powers (Watkins Reference Watkins2005; Kreines Reference Kreines2009; Stang Reference Stang2016; Messina Reference Messina, Massimi and Breitenbach (eds)2017) and dispositions (Massimi Reference Massimi, Massimi and Breitenbach2017; Engelhard Reference Engelhard2018) in contemporary philosophy of science. These scholars argue that the relation between necessitation and systematicity need not be antagonistic. While Kant derives a small set of particular laws from the categories in Metaphysical Foundations, he does not say that lawfulness requires derivation from the categories (Messina Reference Messina, Massimi and Breitenbach (eds)2017: 138). James Kreines (Reference Kreines2009: 528) defines a particular law as a proposition that identifies ‘a kind on whose nature some regularity depends, in the sense that it is necessitated by the nature of that kind’. Several ways of introducing the metaphysical idea can be found in the literature. Eric Watkins (Reference Watkins2005: 244) argues that substances have natures that confer a certain causal power if certain conditions obtain. Nick Stang (Reference Stang2016: 229) draws from Kant’s lectures on metaphysics to frame a similar idea in terms of essences. Kristina Engelhard (Reference Engelhard2018: 8) defines the properties that are relevant for scientific explanations as dispositions. Each presentation shares the view that the lawfulness of particular laws is neither injected into empirical generalizations from above nor projected on them by virtue of the place they take in the best system of laws, but grounded from below. Particular laws can thus be described as categorially contingent and yet metaphysically (i.e. nomically) necessary (Stang Reference Stang2016: 228).

The necessitarian account of lawfulness has clear strengths. In contrast to the best-system reading, it explains how laws govern natural processes. And in contrast to Friedman’s derivation reading, it explains how non-logical relations can be necessary: they are grounded in the properties of objects or relations between properties in nature. Yet several commentators have argued that if the necessity of particular laws is grounded metaphysically – in the real essence of things, which, for Kant, is inscrutable to us (see L-Met/H, 28: 553) – then particular laws are not epistemically available (Kreines Reference Kreines2009: 536; Messina Reference Messina, Massimi and Breitenbach (eds)2017: 138). Critical philosophy rules out essences as the grounds for our knowledge claims. The problem here is that, once the metaphysical grounding of particular laws has been separated from the epistemic conditions of experience, metaphysics cannot be directly reconnected with experience without departing the secure land of truth for the stormy sea of illusion.

The conclusion of nomological ignorance opens several interpretive issues. Pragmatically, it undermines a potential exchange between Kant scholars and causal powers theorists. For causal powers theorists, powers simply are the expressed properties of substances and are fully available to our cognition (Mumford and Anjum Reference Mumford and Anjum2011: 5). As a reconstruction of Kant’s position, it makes it difficult to see why we should seek particular laws in the first place. In this special issue, Lorenzo Spagnesi (Spagnesi Reference Spagnesi2023) argues that, if we cannot have knowledge of empirical laws, it is not clear why we should aspire to know them or how we would go about it even if we tried.

To address these issues, several scholars have pointed to numerous instances in Kant’s critical works where he clearly assumes that there are particular laws, and, moreover, that we are acquainted with them (MFNS, 4: 468; 4: 534; CPR, A766/B794; P, 4: 318; CJ, 20: 203–5; 5: 180–1). They propose alternative necessitarian readings – McNulty (Reference McNulty2015) defends an ‘ideational’ interpretation of Kantian science, Engelhard (Reference Engelhard2018) a ‘broad’ interpretation and Breitenbach (Reference Breitenbach and McNulty2022) a ‘normative’ interpretation – each of which affords ‘knowledge’ (Engelhard Reference Engelhard2018: 9) or ‘cognition’ (Massimi Reference Massimi, Massimi and Breitenbach2017: 169; Breitenbach Reference Breitenbach, Ott and Patton2018: 114) of particular laws.Footnote ⁶ While Kant is clear that real essences are inscrutable to us, he nevertheless states that we cognize many of their essential aspects (L-Met/H, 28: 553). Reason’s ideas guide the understanding in search of the essential properties of empirical objects, such that we can discover the causally salient property by means of a hypothetic-deductive procedure (we come to know, for instance, that sunlight melts wax; A766/B794). As Engelhard (Reference Engelhard2018: 31) puts it, to have a disposition means that a property is essentially linked with a specific causal profile, which confers a causal power. We ‘have full epistemic access to the powers’, she contends, ‘since we know what they do’ (Engelhard Reference Engelhard2018: 9).

A brief overview of the scholarship on Kant’s account of natural laws indicates that broader debates in the philosophy of science have pushed Kant scholars to grapple with the complexity of his account. The necessitarian account of lawfulness opened space for new work on Kant and particular domains of science, for it demonstrates how empirical concepts and particular laws, which cannot be derived from the understanding’s relational categories, can nevertheless be treated as laws. The Lewisian best-system reading led Kant scholars to draw out the regulative use of reason Kant defends in Critique of Pure Reason and to unpack the connections between the transcendental principles that the understanding must ‘presuppose’ if it is to find unity in the manifold of cognitions. Of course, the impasse between the necessitarian and neo-Humean accounts of lawfulness has opened other new positions, including anti-realism (van Fraassen Reference van Fraassen1980) and the disunity of science (Cartwright Reference Cartwright1999; Dupré Reference Dupré2001). Yet as Sabina Vaccarino Bremner (Reference Vaccarino Bremner2023) demonstrates in this special issue, Kant provides an alternative that enables scholars to hold necessitation together with a system of laws that is always under revision. An exciting position that is currently developing simultaneously in philosophy of science and Kant studies emphasizes the role of the human standpoint in scientific inquiry (see Massimi Reference Massimi2022; Spagnesi Reference Spagnesi, Caranti and Pinzani2022).

It should not surprise us that the shifts in Kant studies often track broader currents in philosophy of science. One might of course conclude that Kant scholarship is an isolated field that merely follows broader trends. We propose an alternative view, according to which the scholarship on Kant’s theory of natural science can be seen as part of a broader examination in philosophy of science of the justification we have for assuming lawfulness as a legitimate goal in the first place. Kant scholarship does not always lead to consensus. In fact, it regularly catalyses disagreements. Yet disagreements can nevertheless help us to clarify the assumptions we hold about lawfulness and to test whether we are able to justify them. In the following section we turn to another area of philosophy of science where Kant has periodically made an appearance, especially at moments of disagreement. Exploring how Kant has been utilized in philosophy of biology, we suggest, can help articulate the available positions and evaluate their costs and benefits.

3. Kant and biology

Anyone who has dipped into the literature on Kant and biology will know that it is full of controversies. In this section we show that these controversies track conceptual difficulties that philosophers of biology have also faced – and continue to face – since the Critique of the Teleological Power of Judgement was published in 1790. To do so, we explore the reasons why philosophers of biology continue to appeal to Kant and where these appeals align or deviate from his critical project. We are not interested in policing the acceptable moves one can make under the banner of transcendental philosophy. Focusing on what philosophers of biology are doing when they appeal to Kant, we suggest, can help us to mark out key problems arising in contemporary biological theory.

The controversies in the literature begin with Kant’s relation to the emerging field of biology in the late eighteenth century. While he famously denied the possibility of a Newton who could explain the generation of a blade of grass (CJ, 5: 410), Kant described the problems specific to the investigation of living beings – especially in relation to the Newtonian framework – with uncharacteristic clarity.Footnote ⁷ When he exchanged his work with Blumenbach in the 1780s, the two philosophers seemed to agree that Blumenbach’s conception of the formative drive (Bildungstrieb) was compatible with Kant’s critique of teleological judgement (CJ, 5: 424; Corr, 11: 185). Yet several scholars have since noted that their agreement was superficial, meaning that neither Kant nor Blumenbach interrogated the disparities between their respective projects.Footnote ⁸ These disparities, we suggest, reflect an ambiguity in Kant’s account of organic structure that, misunderstandings aside, has been productive for engagements between Kant scholars and philosophers of biology.Footnote ⁹

The ambiguity we have in mind concerns the epistemic status of teleological judgements. Are organisms governed by an organizational force we come to know through experience, or does the appearance of organized beings merely display the form of judgement we bring to experience? To grasp how this ambiguity can be productive, consider the impact of Timothy Lenoir’s (Reference Lenoir1982) account of Kant’s role in the development of a biological science on philosophers of biology. Lenoir affirms the apparent similarity between Blumenbach and Kant and contends that Kant played an instrumental role in advancing the programme of comparative anatomy, which identifies similarities between organizational forces. Building on Lenoir’s account, several philosophers of biology contend that Kant offers an alternative to the Neo-Darwinian attempt to replace purposiveness with the fitness value bestowed on random mutations by selection pressures. For instance, Lenny Moss and Stuart Newman (Reference Moss and Newman2015: 110–11) note that recent work in the biology of developmental systems raises a problem for Neo-Darwinism. Specifically, it fails to consider the activity of biological individuals, which stabilizes environmental states and thereby affects the selective pressures that act upon them. Moss and Newman propose a re-engagement with Kant’s account of inner purposiveness to develop a new framework for biology capable of extending the range of causal relations at play in the evolutionary process. Now, there is no doubt that Kant’s account of the organism emphasizes the inner purposiveness of living beings. Yet as John Zammito (Reference Zammito2006, Reference Zammito2012) has argued at length, Lenoir’s interpretation fails to acknowledge that teleological judgement for Kant enables us to reflect on certain natural objects as if they were purposive (CJ, 5: 397). For Blumenbach (Reference Blumenbach1789: 25), the formative drive is analogous to Newton’s gravitational force, such that purposiveness marks out an autonomous domain of living beings. While Kant and Blumenbach’s apparent agreement has led several scholars to call on Kant for an extended account of biological causation, it simultaneously underplays Kant’s claim that physical teleology is inseparable from our capacity to judge.

Zammito’s work has assisted Kant scholars to recognize the problems associated with Lenoir’s assessment of Kant’s historical influence. Yet it conflates two questions that, we suggest, should be held separate. The first is whether Kant’s critique of teleological judgement is amenable to Blumenbach’s constitutive account of organizational forces. The answer, Zammito (Reference Zammito2012: 124–7) contends, is that it is not. The second is whether Kant’s critique of teleological judgement can speak to contemporary issues in philosophy of biology. For Zammito, a negative answer to the first question entails a negative answer to the second. Contemporary philosophers of biology aspire to naturalism, Zammito (Reference Zammito2006: 749) claims, and Kant’s attempt to remove Blumenbach’s formative drive from the domain of nature means that he ‘simply cannot be refashioned into a naturalist’. Yet the fact that scholars have misunderstood Kant’s relation to Blumenbach has not inhibited others from making Kant palatable to philosophers of biology. Consider Hannah Ginsborg’s important interpretation, which highlights relevant features of Kant’s account of teleological judgement for the use of function talk in biology. Ginsborg (Reference Ginsborg2015: 251) claims that Kant can help us to maintain the use of teleological judgements without introducing non-natural causes. In what sense, for instance, do we judge a seven-legged horseshoe crab to be deficient? We do not imply that it is morally deficient: that it fails to adhere to a normative standard of what a horseshoe crab must be. There would be nothing irrational about a species of crab that had evolved to have seven legs, or nine for that matter. Rather, we are saying that it is physically deficient: that this individual deviates from the primitive normative conditions that hold generally for its species (Ginsborg Reference Ginsborg2015: 251). Given that a horseshoe crab ought to have eight legs, we ask: why does this specimen have only seven? That answer can be given in entirely mechanical-causal terms. Teleological judgements are indispensable for biology, on Ginsborg’s interpretation of Kant, because they enable us to investigate why a part is or is not there without introducing non-natural forces.

Ginsborg’s interpretation establishes an important connection between Kant’s critical account of teleology and recent literature on biological function. Yet it underplays certain aspects of Kant’s philosophy that may be unpalatable to philosophers of biology. For instance, in the Methodology of the third Critique, Kant argues that moral and physical teleology are connected by a practical belief that humans are ultimate ends of the world (CJ, 5: 431). Our biological and moral ends, he claims, are potentially united by our rational capacity to direct our actions in such a way that we act as if the overall purpose of the world is to manifest the conditions for realising our moral endeavours. In passages like these, Kant seems to be saying more about how physical and moral teleology corroborate one another, despite their differences, rather than how our judgement picks out scientifically interesting phenomena. Ina Goy (Reference Goy, Callanan and Allais2020: 103) pursues this idea by stressing the role of God in Kant’s critique of teleological judgement. In fact, Goy’s argument highlights the connection between Kant’s theological concerns and his denial that teleological judgements form a part of proper science (MFNS, 4: 468, CJ, 5: 400; see Berg Reference Berg2014: 2). While Kant denies that we can have knowledge of God, teleological judgement, by presupposing design in nature, hints at a divine origin. This reason partly motivates Kant to deflate teleology to regulative judgement. When his systematic motivations are laid bare, Kant’s critique of teleological judgement seems to be less relevant to contemporary philosophy of biology.

To defend the relevance of Kant’s critique of teleological judgement for philosophy of biology, scholars generally adopt one of two interpretations. The first interpretation – call it idealism about teleology – emphasizes Kant’s epistemic or pragmatic concerns, according to which teleological judgements do not disclose scientific features of the world. The second interpretation – call it realism about teleology – emphasizes Kant’s clear assertion that teleological judgement is an irreducible condition of biological research (e.g. CJ, 5: 376) and his more opaque claim that teleological judgements are necessitated by empirically given conditions (e.g. CJ, 5: 396).Footnote ¹⁰ Tracing this distinction can help us to see that both philosophers of biology and Kant scholars span a spectrum of interpretations, depending on which aspect of Kant’s critique of teleological judgement they emphasize.

Those who endorse an idealist interpretation tend to hold the view that scientific understanding is incompatible with teleological language. In the Analytic, Kant states that by judging a product of nature teleologically we represent it in a way that does not explain its possibility but elucidates the relation between the whole and its parts by comparing it with another kind of causality we know though our own technical capacity (CJ, 5: 374–5). At best we can explain why we must judge certain natural products according to ends (i.e. to make them intelligible for us), but this is distinct from an explanation of their generation. Teleology thus falls outside the remit of natural science, despite being indispensable for our ability to pick out and examine organized beings. Even Darwin’s conception of natural selection, which explains the acquisition of adaptive traits mechanically, does not escape the presupposition that biological entities, as phenomena, have teleological qualities. For a scientific explanation of an organism to avoid projecting teleological qualities onto nature, it would have to explain a spontaneous, self-catalytic form of organization on the molecular level. As Alix Cohen (Reference Cohen, Callanan and Allais2020: 135) notes, this would potentially reduce biology to a branch of physics and eradicate the distinction between living and non-living beings.

Marjorie Grene and David Depew (Reference Grene and Depew2004) present an idealist interpretation of Kant in their episodic history of biology. On their account, Kant is the first philosopher of biology to identify our subjective need to employ ‘heuristic’ or ‘regulative’ ideas to investigate living beings. Grene and Depew argue that Kant’s resolution to the antinomy of reflecting judgement removes biology from the realm of scientific explanation, for it separates the teleological and the mechanical perspectives at the level of finite rational beings. The upshot of the resolution is that we can pursue mechanistic thinking ‘to penetrate as far as we can into the interior structure of organisms … with little or no fear that we will end up as materialists’ (Grene and Depew Reference Grene and Depew2004: 116; cf. CJ, 5: 413). If we were to attempt a mechanical explanation of the possibility of living beings, we would ‘los[e] our grasp on the entities we are talking about’. On Grene and Depew’s interpretation, the difference between the two maxims of the antinomy is that, while mechanism is the principle of scientific explanation, teleology delineates the biological content of nature in a merely descriptive capacity (see CJ, 5: 412). As we will see shortly, there is a partial convergence with teleological realism here: both interpretations maintain that teleology cannot be reduced to mechanical explanation. Yet in contrast to realists, idealists claim that teleological judgements do not describe irreducible features of nature. Philippe Huneman (Reference Huneman, Goy and Watkins2014: 192) for instance argues that biological functions arise only when we adopt a teleological stance, that is, when we are aware that the entities governed by teleological laws are inherently contingent, enabling us to ask why certain features are present rather than others. On Huneman’s reading, teleology is only applicable to certain elements of nature, whereas mechanistic explanations apply to the whole of nature.

Idealist interpretations are united by the idea that Kant’s critique of teleological judgement removes the tension between judgements of purposiveness and scientific explanation. They generally regard Kant as adopting a unified reductive account of nature, which is incompatible with the notion that functions are real features of the natural world. This might resonate with more recent attempts to justify reductivism, such as E. O. Wilson’s (Reference Wilson1998) return to Whewell’s consilience of inductions. Yet in contrast to contemporary reductive strategies, Kant does not argue that the totality of experience should be reduced to a single scientific explanation. Rather, his account suggests that some aspects of experience fall outside of the domain of scientific explanation. On an idealist interpretation, teleology explains our propensity to deploy purposiveness as a guide for reflection on some natural products at the cost of being able to know their causal origins. For several idealists, this entails that teleological judgement is merely heuristic. Andrea Gambarotto and August Nahas (Reference Gambarotto and Nahas2022: 52) for instance downplay Kant’s claim that it is necessary to judge some things teleologically (CJ, 5: 370) and instead interpret teleological judgement as a heuristic guide employed by biologists when they have certain research questions in mind. Other idealists take Kant at his word. Angela Breitenbach (Reference Breitenbach2009: 32) argues that teleological judgement is an ‘inevitable’ perspective on living beings, even though it ‘introduces a focus that goes beyond any empirical investigation of nature’.

In the past few decades, several teleological realists have appealed to Kant as a precursor to their position (Weber and Varela Reference Weber and Varela2002; Kauffman Reference Kauffman, Henning and Scarfe2013; Moreno and Mossio Reference Moreno and Mossio2015). To show how Kant’s critique of teleological judgement can be relevant to contemporary biology, they argue that discoveries in physics – in particular, the second law of thermodynamics – have resolved the antinomy of reflecting judgement. For instance, Stuart Kauffman argues that what Kant termed ‘natural ends’ are in fact negentropic systems that emerge from entirely natural processes. Biological entities manifest their agency by actualizing functions and can be aptly described as ‘Kantian self-recreating wholes’ (Kauffman Reference Kauffman, Henning and Scarfe2013: 5–7). What distinguishes biology from other sciences is that it is not possible to identify laws that will explain how the biosphere is going to develop. Biospheric development cannot be predicted in advance, for life dynamically adapts to niche environments. Kauffman thus finds no problem with Kant’s claim that there cannot be a Newton for biology who could explain the emergence of a blade of grass. The reason that laws are not applicable for our biological understanding is that organisms (Kantian self-recreating wholes) co-create their environmental niches, which in turn introduce new selection pressures that alter the evolution of the biosphere (Kauffman Reference Kauffman, Henning and Scarfe2013: 16). Of course, an idealist would respond by saying that negentropic systems still require our capacity for teleological judgement to identify them. Given that Kauffman is not strictly interested in teleological judging but in organisms themselves, Kant’s critique of teleological judgement is pushed into the background along with the broader practical questions that motivate his project.

To ensure a productive dialogue between idealists and realists coming from both Kant studies and philosophy of biology, it is vital to pay careful attention to where interpretations of Kant deviate from his original critique of teleological judgement and the consequences of this deviation for Kant’s overall project. Gambarotto and Nahas (Reference Gambarotto and Nahas2022: 54) rightly point out that realists must soften Kant’s insistence that proper science is strictly a body of a priori knowledge and thus cannot be said to be Kantian in a strict sense. Their observation is noteworthy for Kant scholars, as it is the realist interpretations that have received a warmer reception in philosophy of biology over the past decade. In the idealist camp, there is disagreement about whether teleological principles play a merely heuristic role or whether our ability to pick out biological individuals presupposes the principle of purposiveness. Scholars often fail to state whether the disagreement primarily concerns the correct interpretation of Kant’s critique of teleological judgement or the scope of biological theory, leaving some of the most productive encounters between Kant scholarship and philosophy of biology underexplored. Controversies aside, at the very least Kant can help us identify a salient point of agreement between the two camps: idealists and realists both claim that the concept of the organism is indispensable to our investigation of biological individuals. Yet the role of biological individuals in the evolutionary process, and how to carve up nature into discrete biological entities, remains a matter of debate in philosophy of biology.

4. Kant and contemporary philosophy of science

Having noted that Kant’s philosophy – even when misunderstood – can be productive for multiple projects in philosophy of biology, in this final section we consider several recent developments in philosophy of science that have potential synergies with Kant scholarship. First, Kant’s philosophy can offer resources for philosophers who emphasize the importance of values in science. Helen Longino (Reference Longino1990) for instance argues that in science we need to find a common language for the description of experience which would allow us to formulate hypotheses that can be understood by others. Just as Kant understood objectivity as an achievement of the knowing subject, Longino argues that objectivity arises from scientific communities that adopt principles promoting intersubjective criticism. Granted, the mark of scientific objectivity as intersubjective consensus among scientists falls short of Kant’s vision of proper science as a body of a priori rules (MFNS, 4: 468). Yet it stands in proximity to Kant’s broader account of knowledge in the Doctrine of Method, according to which an objectively sufficient ground – such as the agreement of others – is one that we take to be sufficient for holding a proposition to be true (see Willaschek and Watkins Reference Willaschek and Watkins2020). An increasing number of philosophers of science reject the goal of discovering fundamental principles. For instance, pluralists argue that for most scientific developments the Newtonian conception of laws is the exception rather than the rule (Cartwright Reference Cartwright1999: 24; Dupré Reference Dupré2001: 166). They contend that scientific evidence generally tends to oppose rather than confirm the existence of universal laws of nature.

Angela Breitenbach and Yoon Choi (Reference Breitenbach and Choi2017) outline a theory of unified pluralism they describe as a distinctly (albeit distant) Kantian approach to pluralism in philosophy of science. They argue that the benefits of pluralism can only be identified when it is constrained under scientific unity understood as a ‘regulative ideal’ (Breitenbach and Choi Reference Breitenbach and Choi2017: 398). Unified pluralism does not presuppose that an underlying unity of science exists. Rather, it holds that the epistemic virtues of pluralist perspectives can only be realized if scientists adopt the values of collaboration and cooperation. These values encourage scientists to identify how their theories address related problems from different perspectives. Unified pluralism offers an appealing alternative to the dichotomy between unified and pluralist accounts of science. Yet pluralists may resist Breitenbach and Choi’s proposal, for it encourages us to strive towards the ideal of unified science irrespective of the empirical evidence generated to support this idea. On a scientific level, it is unclear what this striving might look like beyond following the recommendation to incorporate the principles of cooperation and collaboration into scientific practice in general. On a pragmatic level, it is unclear how we could know whether our most concentrated efforts at scientific research adopt a regulative ideal of scientific unity. Take the creation and roll-out of vaccines in response to the coronavirus pandemic. The response to the pandemic required unprecedented action across disciplines and organizations, from biochemists to governments. Moradian et al. (Reference Moradian2020) argue that such collective, large-scale action demonstrates the benefits of interdisciplinary approaches similar to those described by unified pluralism, and reveals the need for greater integration both within the sciences and between organizations. Yet the benefits (or relevance) of an overarching commitment to the regulative unity of science for this approach are difficult to evidence. It is more likely that the collective response to the pandemic was targeted to the specific ways that the coronavirus impacted lives on the biological and social levels.

An alternative Kant-inspired view might emphasize the role of intersubjective communication in refining our knowledge and reducing prejudicial bias. For instance, Massimi’s (Reference Massimi2022) perspectival realism proposes that intersecting scientific perspectives guarantee reliable knowledge in line with the Kantian explanation of knowledge of modally robust phenomena without the need to presuppose an obtainable unity of science. Consider again the philosophy of biology, where there is a growing consensus that a single, all-embracing concept of the organism is not only impossible to achieve but also undesirable in practice (see Muszynski and Malaterre Reference Muszynski and Malaterre2021). The prevailing emphasis on genetic mechanisms in twentieth-century biology reinforced the idea that organisms are genetically homogenous individuals. Yet the evidence suggests that genetic homogeneity accounts for a small aspect of life, and there are many more examples of functional integration of diverse genetic lineages through examples such as symbiosis and super-organisms (Pepper and Herron Reference Pepper and Herron2008). The different criteria that scientists adopt for demarcating organisms will provide differing conclusions about what is included in the domain of biology (Clarke Reference Clarke2010). Concerns about our ability to define organisms, or the role of organisms in biology more generally, reignite issues associated with idealist interpretations of Kant’s critique of teleological judgement. In this special issue, Anna Wilks (Reference Wilks2023) argues that the recent emphasis on functional integration over genetic homogeneity should be understood as a process wherein biologists are transforming their regulative judgements about part/whole relationships (or purposes) in nature. Wilks presents a case in which Kant can help us to explain how biologists must first conceive of biological individuals before they become scientific objects of examination.

The recent discussion of model organisms in biology might inadvertently corroborate Kant’s critique of teleological judgement. Rachel Ankeny and Sabina Leonelli (Reference Ankeny and Leonelli2020: 7) claim that ‘[m]odel organisms serve as the basis for articulating processes that are thought to be common across all (or most) other types of organisms’. What is particularly interesting from a Kantian perspective is that model organisms exist at the intersection of artefacts and natural samples. In one sense they are natural; model organisms could not be created in a lab and many aspects of them are not well understood by scientists. In another sense they are artificial, for they are prepared for experimental lab use, which requires selection of relevant traits by researchers. These traits are often preserved over significant time periods and across generations (Ankeny and Leonelli Reference Ankeny and Leonelli2020: 19). To use Ian Hacking’s (Reference Hacking1983) account of scientific activities, model organisms manifest both intervention and representation: they are immensely useful for generating biological knowledge, for they are more easily manipulated in laboratories, and they represent many organisms. From a Kantian perspective, model organisms show that biological knowledge is often dependent on the inferences made by scientists about suitability. We do not passively read biological knowledge from the book of nature, as it were, for in many cases we must actively manipulate organisms for knowledge to be produced. The use of model organisms to generate biological knowledge opens new opportunities for Kant scholarship, for they reveal the importance of social and scientific activities in the formation of biological knowledge.

Growing support for the disunity of science presents new opportunities to explore aspects of Kant’s philosophy in the context of these debates (Dupré Reference Dupré1993; Dupré and Nicholson Reference Dupré, Nicholson, Nicholson and Dupré2018). For disunity theorists, the idea that science is converging toward a single unified explanation of reality not only lacks empirical support, but it also sets a precedent for science that is not reflective of the factors driving scientific development. Angela Potochnik (Reference Potochnik2017) argues that scientific laws do not express metaphysical truths but serve to isolate and idealize specific causal networks. The upshot of Potochnik’s account is that, to understand the development of science, we need to consider the psychological, social, political and economic networks that have contributed to its development; networks that are unlikely to converge on a single unified explanation of all reality (cf. Potochnik Reference Potochnik2017: 208). Potochnik’s broader aim is to demonstrate the challenges for drawing metaphysical principles from science, given that it is inseparable from the various biological and social constraints of being human. Of course, Potochnik is no Kantian, and she opposes the conditions that Kant establishes for proper science. Nevertheless, Kant’s critical philosophy can speak to philosophers who are critical towards scientific realism, for it defends a framework of inquiry that both aspires to unity and yet accepts that a unified science is unachievable. Perhaps we are now learning from philosophers of science that a unified science is not even desirable. In this special issue, Michela Massimi (Reference Massimi2023) highlights Kant’s underlying concern with the societal implications of natural science and its impact on how we understand cosmopolitan rights, which has been undertheorized in the literature. Massimi demonstrates that Kant’s philosophy can serve as a guideline for philosophers of science who embrace a human-centred approach to science and must therefore account for normativity within scientific practice.