A Kantian Approach to Objective Morality and God’s Existence

Abstract

In this article, we explain how Kant upends the terms of the debate concerning the relationship between God’s existence and an objective morality by looking at his moral-teleological argument for God’s existence in the third Critique. We explain Kant’s rejection of external sources of moral normativity and his method of grounding moral authority in the normativity of practical reason. We then turn to Kant’s argument justifying a practical belief in God as the moral author of nature. Kant’s claims about how we must conceptualize organisms teleologically and, as a result, how reason seeks an unconditioned end of nature, brings together our moral purpose with a conception of nature as an organized whole. Since our teleological concepts of organisms seem to require that human beings serve as the final, unconditioned end of nature, but morality and nature might be incompatible and divergent, we must also believe in a moral author of nature. This belief guards against demoralization and creates a unified view of the human moral agent and the world she inhabits, which Kant thinks of as indispensable for our practical lives. Kant notoriously blurs the lines between theology and ethics in nonstandard ways. Although he rejects many traditional approaches to grounding ethics in a conception of divine commands or eternal law, he still devotes a considerable amount of time to discussing the role of religion as a bulwark of the moral life. The goal of this paper is to defend Kant’s relevance to a discussion of the relationship between an objective ethics and the existence of God; his contribution deserves our notice precisely for the ways in which it promises to shift the terms of the contemporary debate and complicate possible answers to the question of whether there can be an objective morality without God. In contemporary philosophical literature, Kant’s argument contending that we must hope in God from a practical point of view on pain of irrationality of acting from duty has enjoyed substantial discussion. Here, however, we focus on a lesser-known suite of arguments that in order to so much as cognize ourselves and other species as the sorts of natural beings they are, we must believe in a supersensible moral author of these natures. This set of arguments ultimately dovetail with the more well-known argument for theistic hope and operate in much the same way. But they touch on facets of Kant’s whole philosophical system, such as his account of teleological judgment and the unity and final end of all of nature. Our goal is to explicate these arguments and illuminate their relevance of these Kantian arguments to the debate about the relevance of God to objective morality. We will argue that while an objective ethics is possible without God due to the active role of practical reason in rational agents, belief in God’s existence strengthens the claims of morality, both for psychological reasons but also by providing a more unified conception of moral and natural reality.

1. Objectivity in Kant’s Moral Epistemology

To appreciate Kant’s view on this matter, first we need to survey some of the epistemological assumptions operative in his broader philosophical project. These epistemological assumptions are worth considering, as they rule out a few major competing bases for an objective ethic and help to explain what motivates his turn to the normativity of reason itself to ground morality. The Kantian basis for an objective morality does not reference God’s existence. The Kantian account of morality is shaped by epistemic problems with which Kant is concerned in his larger critical project, especially from his critique of theoretical reason in the Critique of Pure Reason. There, he famously rejects theoretical arguments for God’s existence, including the ontological argument, cosmological argument, and physico-theological argument.1 These arguments lead to a position according to which God’s real possibility is indeterminate and cannot be established conclusively from the standpoint of theoretical reason.2

Kant’s epistemology developed in the first Critique holds that all cognitions must include both a concept of the understanding and sense experience (sense intuitions, as he calls them).3 As a supernatural entity, God cannot be experienced through sense intuitions, nor is God experienced in the pure intuition of space and time. Thus, no cognition of God is possible. It also follows from his epistemology that any cognition we have is mediated through a priori concepts of the understanding without which we could not organize and make sense of our experiences.4 Our cognitive faculties play an active role in bringing concepts together with sense information to form cognitions of objects in the external world. This means that we do not have unmediated access to such objects in themselves but only as appears to our cognitive faculties. This will create difficulty for seeing how experience can be related to moral knowledge.

From the theoretical standpoint, then, our epistemological position vis a vis God’s existence is precarious. Even if God’s existence could fully ground morality, such a grounding would not be one in which we could be confident from the standpoint of theoretical reason. This leads Kant to seek an alternative account of the grounds of the moral law.

Kant thinks morality must not be contingent, as sense experience is. The very concept of the moral law, rather, indicates that morality is categorical or necessarily binding on the will.5 Likewise, it cannot bind from without or from some external source, or else it would not bear the special form that gives the moral law its unconditional normative force.6 One could escape the normative power of a law, which was imposed by an external condition, so long as one could escape being in that condition. The motivation here to claim that the will is the source of its own lawfulness seems like a common one—freedom is a prerequisite for any sort of moral worth or moral responsibility. External forces acting directly on the will do not constitute rational or intentional action. Thus, the only subject eligible for moral praise (or blame) is the agent who acts with freedom.

Kant has a further concern about the determinism of the external world insofar as it appears to us. We examine the natural world and the operations of external reality with the presumption that it is a closed system of cause and effect.7 This presumption affords us incredible advancements in scientific understanding and technological development, of course, and social sciences often engage in efforts to describe human action according to such cause-and-effect patterns (consider evolutionary psychology and accounts of moral psychology as adaptive rather than tracking moral truths). How, then, can we understand ourselves and others as free, rational agents?

A few paths are possible: First, we could concede to determinism that human behavior is likewise subject to the cause-and-effect matrix and, thus, reconceive moral evaluation in terms of subjective preferences, sentiment, or habit.8 This would be to grant that there is nothing distinctive about moral judgments or prescriptions; these are merely continuous with nature. Setting to the side a robustly objectivist naturalism, given the difficulties of defending such a position, we might say that morality and moral judgments are part of the natural world but are subjective; they can be reduced to human desires or commitments. This route will not do for Kant. For Kant’s task is to find out whether an objective ethic is possible, and if so, what its shape must be.

The second path leads to the idea that an objective ethic is possible but may need a richer metaphysical or theological story to understand how nature is imbued with normativity. The Aristotelian version of this story rejects causal determinism and insists that normativity is already embedded in the natural world, as biological organic life already is viewed as teleological, metaphysically.9 Norms are given to us via observation and natural inclinations. In addition to the contingency of such moral knowledge and its relation to the somewhat unreliable inclinations, there are remaining epistemic difficulties for this solution.

A third path views something external to the natural world, such as divine commands, as the source of moral normativity. But positing divine commands as a source of morality will be problematic in the Kantian system for multiple reasons. There is doubt about the universality of these commands and their promulgation through history.10 If these commands are supposed to motivate the agent by inciting fear of God as a lawmaker, especially as having the capacity to punish wrongdoing, then it seems the agent is motivated to the right thing for the wrong reasons, heteronomously and contingently. And agents might reject divine authority, as it seems possible to act as an agent without recognizing the demandingness of God’s commands.11

Kant seeks to establish an objective ethic through reason’s own intrinsic normativity spelled out in the categorical imperative. This includes the imperative to universalize one’s own maxim, allowing for harmonization with the wills of all other agents: “So act that the maxim of your will could always hold at the same time as a principle in a giving of universal law.12 Practical reason, grounded in the autonomy of the will of rational beings, is an unconditioned and active principle in Kant’s view. A rational being possesses the capacity to “legislate” the moral law to herself in a way consistent with the freedom of all other moral agents.13 This makes the normativity of that law intrinsic in just the way Kant supposes morality’s normativity must operate. Reason’s very form demands that we act in certain ways and refrain from other types of actions. These prohibitions and requirements just are the prohibitions and requirements of morality—the laws to which a person with a good will conforms their activities.

2. The Relevance of God

The arguments thus far seem to indicate that God’s existence is irrelevant to an objective ethic of the sort Kant seeks. Reason alone establishes the validity of the moral law—and it is the only thing suited to establish it. Yet, as Kant scholars have noted, Kant goes on to make some surprising claims about the relationship between God and the moral law (See, for example, Chignell 2023; Hare 1996, 2011; Kain 2005; Ebels-Duggan 2016). We will briefly survey some of his arguments that move from morality to “Belief” in God’s existence.

Importantly, Kant uses a special word here for Belief (Glaube) to indicate that this is a proposition justified on the needs of practical reason, not theoretical reason. This means that the proofs do not transfer into metaphysical or dogmatic claims about God’s existence, leaving them somewhat tenuous. However, from a practical point of view, Beliefs in this sense hold great significance; they are the postulates we need to assume to make our everyday deliberation possible. In the terminology of contemporary metaethics, theism of a very particular sort is deliberatively indispensable.14

Kant’s well-known practical arguments for Belief in God rest on the separation between virtue and happiness.15 Virtue is the condition of having a will conformed to the moral law. Happiness includes the fulfillment of all our animal incentives as far as is possible in accordance with what the moral law prescribes. In the second Critique, the argument is built upon our duty to promote the Highest Good—the state in which virtue (the worthiness of being happiness) is in fact tied to happiness.16 This duty is established through independent arguments, though the argument to promote the Highest Good as a combined state, and not just to fulfill the demands of virtue, is not very clear. Given the principle of ought implies can operative throughout Kant’s moral philosophy, if we have a duty to promote the Highest Good, then we have to think this state of affairs is actually possible. We must presuppose God’s existence, then, to make possible the Highest Good.

In the first and third Critiques, the argument does not rest on this tenuous duty to promote the Highest Good. Instead, it concerns itself with a question Kant first raises as part of his goal of the critical project, “What may I hope?”17 Reason does not prompt us to promote the Highest Good as a duty. Yet, as animal beings who do not wish to think their inclinations and being directed towards embodied happiness are in vain, we surely cannot let go of the hope that virtue will be rewarded with happiness. If we have a genuine hope that the Highest Good is possible, then we must presuppose a Belief in the real existence of God.18

Kant argues that this hope is not merely wishful thinking but is a psychological need of practical reason (For further discussion, see Chignell 2023; Sweet 2023). It guards against demoralization in which even the most dutiful person in the world would eventually lose moral resolve to fulfill their duty.19 Although moral knowledge is accessible to all practical reasoners independently of knowledge of God’s existence, the fact that humans are finite rational beings makes us susceptible to demoralization. Thus, there is a sense in which for us as human beings, God’s existence is psychologically necessary for us to presuppose in order to maintain the force of an objective morality.

Taking stock: so far we have explained that Kant rejects the possibility of confident theoretical belief in God, since the very idea of God excludes one of the components of every one of our proper objects of cognition—the sensible. At the same time, Kant defends the rationality of a form of belief in God from the practical perspective. We can understand the latter kind of argument as an argument from the indispensability of Belief in something only God could bring about—a world in which action in accordance with duty is rewarded. Further, Belief here functions differently from ordinary epistemic states governed by theoretical norms. This sets us up to understand what we suggest is a distinct and underappreciated, though related, line of argumentation in Kant’s third Critique.

3. A Moral-Teleological Argument: Part One

In the third Critique, Kant develops a moral-teleological argument for God’s existence that operates in much the same way as the practical argument for hope in God we looked at in the previous section (and, on our reading, is related to this argument). But in the moral-teleological argument, Kant derives the necessity of Belief in God from a series of claims about both human life and the natural world. The argument proceeds in two parts, the first of which we will examine in this section.

The moral-teleological argument begins with observations about how we do and in fact must think about organisms, both human and nonhuman. When we look around at the world, we can understand ordinary objects as organized. Many such objects have, as their principle of organization, an end imposed on them by whoever made them. We look out the window to see a bicycle, for instance, and we understand both that the wheels are part of the larger vehicle and what the wheels are for because we know that humans have constructed bicycles for the purpose of smoother, swifter transport than walking. The materials that compose the coffee cup on the table do so because the local potter at Black Oak sat down and spun the clay to form a mug that would keep coffee warm and allow a human hand to grip it comfortably. This all makes sense according to what Kant calls a “mechanical principle.” The external cause imposes the form on the object and gives it an organizing principle.

But individual organisms, humans included, are not like this. We cannot locate the source of what holds them together and makes them operate as they do within nature—that is, within the world we sense. The robins flying outside the window have done so since before we existed, and they do not build their nests for our sakes. Nor is it clear what explains why we are organized, as human beings, as the sorts of self-sustaining organisms we are. An explanation for the organization we cognize when we think of a living thing in general, and humans in particular, requires an appeal to something outside the sensible realm, according to Kant. We are led on to the concept of an author, or artificer, of nature, analogous to the builder of the bicycle or the sculptor of the coffee mug.

Individual organisms must be thought of in accordance with the teleological principle under the concept of the parts as oriented towards the whole.20 For example, we could not understand what a heart is without understanding that it is part of a larger self-sustaining organism and that it plays a vital role in pumping blood and oxygen throughout the body of the entire organism. The heart only develops at a certain stage in the organism’s life cycle in order to fulfill this function. If nature only operated according to mechanism, we would not expect that the development of the whole organism would drive the development of individual parts in this way. Rather, there would simply be aggregates of parts.

An organism, according to Kant, is a “natural end”—its purpose does not come from something outside the organism itself and its life cycle and activities. Kant elaborates: “I would say provisionally that a thing exists as a natural end if it is cause and effect of itself.”21 We can grasp his meaning here by contrasting organisms with artifacts. Whereas an artifact’s end must come from something beyond itself, a natural organism seems to engage in the operations and activities it does in order to maintain itself and those very activities and operations. There are no spontaneous artifacts that are what they are simply because of themselves and nothing else; instead, their purpose and what they are both must refer to a maker of the artifacts. We can also contrast these internal purposes of nature with extrinsic purposes of nature that a rational agent imposes on organisms, such as human use of domesticated animals for labor or use of a river for communication.22

Further, as Naomi Fisher explains, for organisms but not for artifacts, “parts and whole are mutually dependent,” (Fisher 2023, p. 168). Imagine I am building a bike; I acquire two wheels, tires, a frame, handlebars, cable and housing, a cassette of gears, crank, pedals, and derailleurs. Each of these items can be described without reference to a bike. The cable and housing could just as well be used for hanging a drying rack in my backyard. The gears and crank might have been put to work in a grinder or a tiny mill. The tire tubes could be used for any number of other types of vehicles. By contrast, what it is to be an eye or an arm or a heart must refer to the whole organism and its operations at the level of the whole. Apart from their operations in a body, we cannot understand properly what it is for the eye, arm, heart to be what they are.23

Our cognitions of ourselves and other species as organic wholes helps us to understand various objects as parts. For instance, by grasping some principle of organization in a bird, we can understand the hollow structure of the bones as serving the purpose of swift flight. Contrast this with finding out that the bird’s bones are white. The color of the bones is incidental. Yet, to make such a distinction is already to have in mind what Kant calls a “nexus effectivus”—something that arranges and unifies all the different parts and operations of the bird and makes it the sort of thing that it is.

Yet Kant insists that reason will seek a further explanation of the unity of such organisms:

For if one adduces, for example, the structure of the bird, the hollowness of its bones, the placement of its wings for movement of its tail for steering, and so forth, one says that given the mere nexus effectivus in nature, without the help of a special kind of causality, namely, that of ends (nexus finalis), this is all in the highest degree contingent: That is, that nature, considered as mere mechanism, could have formed itself in a thousand different ways without hitting precisely upon the unity in accordance with such a rule and that it is therefore only outside the concept of nature, not within it, that one could have even the least ground a priori for hoping to find such a principle.24

The problematic set up here shows that when reason cognizes an organism, it presumes that there is some principle of unity which could not be explained mechanistically. Thus, the form of our cognition requires an explanation in a teleological order—a purposive explanation. And for this, Kant insists, we must look to something outside of nature—something “supersensible,” in his terms.

Kant recognizes the tendency to want to connect teleological judgments about organisms to a divine artificer of nature. A simple “physico-theological” argument might be formulated around this conception of organisms:

• We judge ourselves and other creatures as organic, self-sustaining wholes.
• The principle of mechanistic causation within nature does not suffice to explain this intelligibility of organisms as organic, self-sustaining wholes.
• The intelligibility of the concept of an organic, self-sustaining whole depends on the concept of an end, which serves as the principle of organization (and this principle of organization we can call rational, on analogy with moral action according to ends or the creation of artifacts according to the concept of the whole).
• Any end internal to nature cannot explain fully the unified rational principle of organization of an organism—reason must operate freely of the determinative causes within nature.
• Therefore, we need an end external to nature—supersensible—to explain fully the unified principle of organization of an organism.
• So, the intelligibility of our cognition of ourselves and other creatures depends on the concept of a rational, supersensible end.
• For there to be a supersensible end requires a supersensible author of the natures with ends in the supersensible and nonmechanistic order.

The conclusion of this argument is that our teleological judgments depend on a supersensible artificer who serves as a principle of organization for organisms and indeed the whole of nature.

These arguments, as we have characterized them so far, do not make obvious any connection between moral authority and God. We might object that the supersensible author of nature could be a nonmoral supercomputer and organisms could be simulations in the computer, for instance. If that were possible, then we might view as incidental that humans—beings that operate fundamentally under the concept of moral freedom—serve as the supersensible ends of nature and that the supersensible author of nature is a moral being, namely God.

Moreover, we will see that there is a remaining difficulty for the first premise about our teleological judgments of organisms in that they are not meant to represent how organisms are in themselves but are only intended for the reflective judgment.25 To overcome these limitations of a purely physico-theological argument, we must return to the insights of practical reason and look towards Kant’s enhanced moral-teleological argument. As a result, the above physico-theological argument in isolation still leaves an “incalculable gulf” between nature and freedom.26 Without a moral author of nature, our moral purpose may have no shared author with the natural world and, as a result, would leave us without a physical place in which we could have hope of embodying our moral purpose as sensible and moral beings. Since Kant intends for his third Critique to bridge just this gap between nature and freedom, this would be an unsatisfying place to land. Judging organisms teleologically is a first step towards this unity of freedom and nature but cannot get us the whole way since we only judge organisms teleologically in a limited way. So, the moral-teleological argument to establish God as the moral author of nature will be the next step towards this unity.

4. The Moral-Teleological Argument: Part Two

We must keep in mind the limited scope Kant intended for these teleological judgments. He relegates these judgments about organisms to reflective judgment rather than determinative judgment. Importantly, the principle of purposiveness is synthetic a priori; that is, teleological judgment is “rightly drawn into our research into nature, at least problematically, but only in order to bring it under principles of observation and research in analogy with causality according to ends, without presuming thereby to explain it.”27 We presuppose a kind of teleological unity in biological organisms in order to make research into their parts and their functions intelligible. Nevertheless, Kant does not think that this principle gives us insight into organisms in themselves. This is related to what was explained earlier about Kant’s caution about any empirical insight into the nature of things in themselves. Theoretical reason in its empirical application is always subject to mediation through our cognitive apparatus. Here, though, we are even more aware that we are supplying the principle of purposiveness a priori into our research of nature. So, we must not move too quickly to assuming that our teleological conceptions of nature represent metaphysical judgments about organisms or the final purpose of nature as a whole.

Nevertheless, the reflective judgment is justified in adopting this teleological principle to make intelligible individual organisms because no other principle will do. And we have to cognize organisms, including ourselves, so we must adopt this principle. Once we are justified in adopting this teleological principle into our research of nature, reason is able to consider whether this unifying principle applies not just to individual organisms, but to the whole of nature as an interconnected system.

In considering this, Kant distinguishes two senses in which the principle of purposiveness might be applied to the whole system of nature. This results in the distinction between an ultimate end of nature and a final end of nature, the former being an end within nature—the end towards which it is developing through causes internal to itself.28 Nature itself will always be sensible and, as a result, conditioned. Hence, this ultimate end of nature internal to itself will not meet the highest demand of reason for an unconditioned end. So, reason continues to seek what Kant calls a “final end of nature”—an unconditioned end of nature that could only be unconditioned by being external to the system of nature as a whole.29 This is what Kant considers “supersensible.”

For Kant, human beings are fit to serve as the end of nature in both the ultimate and final senses. As animal beings, we clearly are a part of the system of nature and its nexus of causes. Much of our knowledge relies on sense perceptions acting on us from the outside. Our inclinations and desires are shaped by physical causes often beyond our conscious control (even if there is some control we are able to exert over them), including environmental features and responses towards objects of inclination. And not only are we individually affected by natural causes, but the development of human beings qua species can be viewed as mechanistically determined by the causes of nature. For example, Kant often describes the deterministic forces of history that lead human culture towards our moral destiny in ways that circumvent our practical agency. Consider this passage from Kant’s essay on “Perpetual Peace”:

Perpetual peace is guaranteed by no less an authority than the great artist Nature herself (natura daedala rerum). The mechanical process of nature visibly exhibits the purposive plan of producing concord among men, even against their will and indeed by means of their very discord… We cannot actually observe such an agency in the artifices of nature, nor can we even infer its existence from them. But as with all relations between the form of things and their ultimate purposes, we can and must supply it mentally in order to conceive of its possibility by analogy with human artifices.30

Here, “perpetual peace” refers minimally to a state of affairs and a political climate that is consistent with the moral law and the possibility of human happiness. So, it entails the realization of our moral purpose as rational beings. From the viewpoint of the ultimate end of nature, though, nature itself works towards this end without our free cooperation.

As moral beings—this being established, again, through independent argumentation—human beings have freedom that is unconditioned. This is just what it means to be an autonomous agent, to act according to concepts and determine one’s own will internally. As embodied animal beings, such determination of our wills must serve as the efficient cause of our embodied action. That is, our moral action must be a cause of what actually occurs in the sensible world; we must have the capacity to shape the physical world according to what we will, though not in an unlimited sense. The content of the moral law prescribes that we shape our environment and social institutions according to what practical reason wills universally. This is the sense in which Kant not only identifies the ultimate end of nature as the human being, but more specifically human culture. From the standpoint of us as moral beings, culture is a state of our own making and universal moral legislation (ideally in a republic or similarly structured state).31 Through the development of human culture in history, we actively create the social and political context in which morality is actualized.

An important thing to emphasize here is that we would not be able to justify the conception of human beings as the ultimate and internal end of nature if we did not have the practical knowledge of the supersensible within us. So, it is actually the fact that human beings have independent knowledge of our moral purpose and are thereby acquainted with the supersensible in our own beings that we can then adopt a view towards human beings as the ultimate and internal end of nature. Of this moral purpose, “it cannot be further asked why it exists,” as this moral nature has an autonomy and a worth that is an end in itself.32 As Kant remarked in the “Perpetual Peace” passage above, nothing in our experience of nature could justify the conception of it working towards this moral goal. It only results as a consequence of seeing that human beings are the only creatures in nature that could supply a supersensible end to satisfy reason’s desire for an unconditioned purpose for nature. Our practical reason, then, plays a major role in our conceptualizing nature as a system with its own ends, both external and internal (for discussion see Fisher 2021, p. 82).

We can now consider what conceiving of nature as having human beings as a final and ultimate end does for the moral-teleological argument. Imagine if nature only presented itself to us under mechanistic laws. We might still be able to think of ourselves as free moral agents from the standpoint of practical reason and its dictates. But reason would be left with the incalculable gulf between freedom and nature, our moral and animal parts. The moral argument from hope argues only from the need to guard against demoralization from the practical standpoint to practical Belief in God’s actual existence. Here, however, we have theoretical justification to adopt a principle of purposiveness into our research of nature via organisms. We find that theoretical reason’s desire to extend this principle of purposiveness to nature as a whole aligns well with and is completed by practical reason’s unconditioned nature. And practical reason further has the need to adopt theoretical beliefs about human beings as the ultimate end of nature in order to see our moral purpose as carried on by nature. Belief in an author of nature that ties together the final and ultimate ends of nature can also guard against demoralization and a disunified view of the human person. So, Belief in God is justified via the principle of purposiveness in conjunction with practical reason.

5. Why a “Moral” Author of Nature?

To see the connection of this line of reasoning with the moral argument for God’s existence, it may be helpful to recall two of Kant’s claims about the conceptual connections between agency, morality, and rationality, versions of which are articulated in contemporary metaethics under the headings of Constitutivism and Moral Rationalism. In doing so, we can shed light on the relationship Kant thinks holds between the condition on the possibility of our judging organic unities and our Belief in God as the moral author of nature. We will leave discussion of how this reinforces Kant’s more well-known moral argument for God to the next section.

Kant maintains that the very essence of practical agency—of beings who must act from choice—consists of our rationality. One way to understand this practical rationality in contemporary metaethics is to say that without having and exercising the ability to reason about what considerations bear on how we should act, we would not be agents acting at all. And, in more contemporary philosophical parlance, reasons are “simply those demands to which we are subject insofar as we are the kind of thing that we are essentially.” (Smith 2015, p. 194). These conceptual truths guarantee Constitutivism:

Constitutivism: Anyone who performs an action is subject to the normativity of rationality; that is constitutive of what it is to act as an agent at all.

There is a weaker and a stronger way of understanding Constitutivism. In the strong version popularized by Christine Korsgaard (1996), actions that do not meet this reflective standard at all do not even qualify one as acting as an agent. In the weaker version, it is our having the capacity for reflection upon reasons for action that makes us subject to their demands, whether or not we actively reflect upon such reasons for a given action. Given that contemporary Kantians disagree about which interpretation accurately reflects Kant’s views, we will think about Constitutivism here in a manner consistent with both of these readings.

Practical reason, action, and agency together form a tight conceptual circle on Constitutivism. In the weak version, agency must be defined in terms of a capacity for practical reasoning in a certain way. In Kantian terminology, as practical reasoners, we cannot help but consider ourselves under the law of reason—on the strong version—or a condition of the possibility of our agency is the ability to so consider ourselves.

Notice, then, that the supersensible author of nature must also be governed by the normativity of rationality in order to exercise agency in creating the universe and creatures. The author of nature acts for the sake of an end. But if Kantian Constitutivism is true, then that author has to be an agent with practical reason and under the law of reason. This is the reason Kant identifies the content of the moral law with God’s will in the second Critique.33 Since God is perfectly Holy, God is not obligated by the moral law in the way that sensible beings are. God does not have a competing sensible nature that might be taken up into practical maxims in a way that conflicts with the demands of practical reason. But as the rational author of nature, God’s will is perfectly aligned with the moral law.

Now we can piece this together with another of Kant’s commitments, Moral Rationalism. Kant espouses the view that the domain of morality just is the domain of normativity of practical reason. Unlike the divine command view, God’s will or command is not necessary to generate the normativity of moral obligations. The lawlike structure of morality is built into the dictates of reason, whereas this structure cannot be read off God as lawgiver necessarily. Nor can we start out assuming that nature is imbued with normativity, such that one ought to fulfill one’s own nature, in Aristotelian fashion. Reasons for action and moral reasons are not just coextensive; all decisive reasons are moral reasons. For morality and practical rationality are identical. The moral law can be understood as an expression of the form of practical reason, that which rational beings are subject to at all times in virtue of their rational natures.

What does this imply regarding the moral-teleological argument? We have seen that Constitutivism enables us to move from the conclusion of the first part of the argument to the claim that the supersensible author of nature is a practically rational agent. The act of creating organic unities for the sake of a final end depends on the existence of such an agent to perform the act. The only kind of agent, in Kant’s view, who could perform such an act is an agent who responds to all and only the reasons for action there are—that is, a perfect moral agent. Further, this sort of agent wills free, rational beings (humans) as the final end of nature. Freedom is how Kant characterizes the activity of a will that acts in accordance with the normativity of practical rationality, that is, in accordance with the moral law.

Let us bring together the various strands of the moral-teleological argument. Kant wants to show that conceptualizing nature as organized by unifying principles demands that we can think of natural beings as having a certain form, and that form is teleological. If we can make the further claim that there is a final end of nature, and practical reason tells us that our moral natures are just such an end in themselves, then nothing could produce or explain this purposiveness of the whole system of nature except a supersensible being acting for the sake of a final end, that is, exercising practical reason. And this agent must exercise practical reason in such a way as to produce a world where the various creatures and their ends are compossible and in harmony because of a mega-purpose. It follows that a condition of the possibility of our cognition of ourselves and other creatures is a supersensible moral author of nature. And no being can play that role but God.

This moral-teleological argument functions as a kind of deliberative indispensability argument. Some contemporary metaethicists, like David Enoch, argue that we must treat certain moral properties or entities as real in order to deliberate at all (or to engage in genuine moral disagreement). The Kantian argument we spell out above does not purport to derive an epistemic justification for ordinary theoretical beliefs in some entity or property on the basis of its indispensability to deliberation about particular actions per se. Instead, it starts with the fact that we do and must regard ourselves and other life forms as having a certain principle of organization—otherwise we cannot understand our parts as parts or our activities as functions at all. And such teleological judgment is necessary to our action in the world. The necessity of such teleological judgment makes whatever conditions the possibility of that judgment an object of practical belief. What turns out to be indispensable, moreover, is not a kind of moral property but a type of agent—the moral author of nature. And since God is the only eligible agent to be a moral author of nature, we must regard God as real from the practical point of view.

6. Connections with Kant’s Better-Known Moral Argument

Like the more well-known argument from Hope, the moral-teleological argument is established for the use of practical reason and not for merely theoretical belief in the existence of God. It serves, therefore, to bolster our moral purpose. As Kant says, teleological judgment “urges attention to the ends of nature and research into the inconceivably great art that lies hidden behind its forms in order to provide incidental confirmation from natural ends for the ideas created by pure practical reason.”34 The fact that we can now see our moral purpose and nature as unified by a moral author allows us to strive more ardently towards the Highest Good. From experience alone, there are many ways in which the natural world itself often seems at odds with our moral purpose. For example, in Kant’s discussion of the sublime, we see natural features that seem outright “contrapurposive”—powers such as lightning, volcanoes, hurricanes, and other natural disasters that render our physical strength and sensible faculties quite useless. While the sublime allows us to raise ourselves above such naturally overpowering phenomena by making us aware of our dignity residing in the supersensible, such powerful natural forces have the potential to overwhelm with fear and prevent us from that moral feeling of respect for our moral dignity over nature.35

The point is that human beings, as both sensible and moral beings, are peculiarly subject to demoralization in the pursuit of our moral duties and to a disunified view of ourselves. Viewing God as the moral author of nature can help reinforce our dignity against such a view that sensible nature is overwhelmingly opposed to the projects of human beings. We can view the Highest Good as something not only possible but also as something that nature positively contributes towards, as outlined in the example from “Perpetual Peace.” Unlike the argument from Hope, however, this is not established merely through practical reason. The fact that theoretical reason itself justifies our adoption of the principle of purposiveness allows for a greater unification of theoretical and practical reason.

7. Conclusions

Our aim in this essay has been to highlight how Kant’s moral-teleological argument contributes distinctively to the contemporary debate about whether a version of theism is required to support an objectivist account of morality. Kant, of course, has his own view of what an objective ethic must look like—a view many will not accept. But Kantian approaches to morality have gained traction in contemporary philosophy in no small part because they put forward a version of moral objectivity that seems plausible given our best science.

The Kantian idea that we need to engage in teleological judgments to make sense of organisms, including ourselves, resonates with contemporary philosophy of biology and some recent versions of ethical naturalism as well (for instance, see Moosavi 2018, 2022). So an argument that operates on these dual assumptions may be more welcome than other forms of moral arguments for God’s existence.

Kant’s moral-teleological argument offers a way of justifying practical belief in a specific form of theism, namely, the view that God is the artificer of all of nature and creates human rational agents as the end of nature. A theism that includes this view can support the sorts of teleological judgments we must make to operate in the world as we do. So much the better for such a variety of theism. This second Kantian argument, moreover, can be seen as underwriting the more well-known Kantian argument for practical belief in God. Thus, it deserves our serious consideration.