This book tries something new. It attempts to put two philosophical literatures, namely Kant scholarship and environmental philosophy, in conversation. What could these two fields share? Are they not miles apart? The first studies influential ideas from the history of philosophy, often applying those ideas to debates in contemporary ethics, metaphilosophy, epistemology, and the philosophy of science. The other commonly asks axiological questions about the relationship between nonhumans and nature. Kantians mainly care about what is human. In the exhaustive encyclopedia The Kantian Mind (Reference Guyer, Baiasu and Timmons2023), respected Kant scholar Paul Guyer even refers to Kant’s philosophy as anthropocentric philosophy par excellence.Footnote ¹ If environmental philosophers seek to go beyond human-centric worldviews – to showcase the limitations and inadequacies of anthropocentric philosophies – then is this book not hopefully misguided? Is it a futile exercise to link two incompatible fields? Please join me for a little bridge-building.

As mentioned, the present book attempts to do something novel. Part of this novelty has to do with the relative dearth of contributions in environmental ethics and environmental philosophy that take Kant’s philosophy seriously.Footnote ² To be sure, as we will see, environmental philosophers do spill ink criticizing Kant and his legacy. We will examine their complaints in due course. Yet the times are changing. Historically, environmentalists were concerned with questions about topics such as pollution, conservation, wilderness, and the aesthetic value of nature (Norton Reference Norton1991). With human-caused climate change on the scene and the stability of the Holocene threatened, environmental philosophers have begun to shift their sights. Though climate change is hardly the only environmental challenge of our age, it certainly bundles them into one neat package. Failing to grapple with the climate crisis worsens prospects for other environmental philosophy interests, including biodiversity protection, nonhuman animal welfare, and more. It is thus prudent for those who care about the environment to orient their focus on the crisis. Yet where does this leave Kantians? Besides insights in theoretical philosophy, Kant’s legacy includes his immense contribution to practical philosophy, including ethics, legal philosophy, and political theory.Footnote ³ Aspects of Kant’s practical philosophy have been influential even for nonphilosophers, with his normative impact on political science, international law, and theories of human rights being especially relevant in 2024.Footnote ⁴

The problem is that, at least on the standard and most commonly received reading of Kant’s practical philosophy, he is only concerned with humans. Sure, nonhuman animals matter in a roundabout sort of way. That is, we have, as Kant puts it, indirect duties with regard to animals (MS 6:443). And, in addition, it is true that Kant in his ethics and political philosophy suggests we should care about broader environmental stability at least instrumentally, as a means to secure the independence of human persons and the stability of the Kantian political state (MS 6:325). Many environmental philosophers will nonetheless see these as unstable beams, indeed a reason to abandon the bridge frame. We need to value nonhuman nature – organisms, ecosystems, the earth-system itself – to face our environmental crisis head-on; Kant, they argue, could at best justify a humanist “imperative of prudence” amounting to shallow ecology (Dumas Reference Dumas, Drenthen and Keulartz2014, 75). This is not the thing we need.

In addition, Kant’s ethical theory seems hopelessly committed to a deontological framework ignorant to the consequences of actions. Even if Kantians and environmental philosophers could, as this book will argue, find common ground in uniting to face the climate threat, surely Kant’s nonconsequentialism makes him a weak resource for thinking about how to respond. This is because thinking about the crisis requires taking risks, impacts, projections, and other hazards seriously. These seem better suited to consequentialist thinking,Footnote ⁵ not to mention the need for a collective and intergenerational paradigm shift (Gardiner Reference Gardiner2011). It comes as little surprise that environmental ethicists like Dale Jamieson (Reference Jamieson2007) rebuke Kant’s philosophy, not only for his anthropocentrism, but for his nonconsequentialism and his individualism.

Many environmental philosophers look to the modern philosophical canon with a negative eye. Val Plumwood (Reference Plumwood1993) and Steven Vogel (Reference Vogel2015), for example, see dualisms in these traditions that motivate the conceptual separation of humans from nature. In their objections, they explicitly impugn Kant and his legacy. Why should we appeal to a theorist like Kant, whose ideas are part of the cause of the crisis, they ask. While René Descartes and Francis Bacon are usually the first targets in this endeavor, it is unsurprising that their successors in the modern tradition – Kant, Hegel, and Marx – receive flak. At the same time, since philosophers outside environmental ethics have begun to appreciate the immensity of the climate challenge, there has been a new movement in attempting to “green” the philosophical canon. This greening procedure involves ecological rereadings of canonical philosophers, or new perspectives on their prescient insights for a sustainable future. Accordingly, even Hegel and Marx have been commissioned by commentators (Schultz Reference Schultz2020; Saito Reference Saito2023), while those preceding Kant like Leibniz and Spinoza have received similar treatments (Phemister Reference Phemister2016; Stephano Reference Stephano2017). I do not assess the merit of these accounts, though I stipulate for the sake of this book that insights of canonical philosophers may prepare us for obstacles ahead.

This is the first monograph-sized analysis of the relevance of Kant’s philosophical views for environmental issues, especially as these relate to the Anthropocene.Footnote ⁶ In it, I am interested in the extent to which a Kantian perspective can guide us amid, as Byron Williston puts it, the “battle for a humane Anthropocene” (Williston Reference Williston2021, 108). One reason that helps explain the lack of green Kantian perspectives – whereas greenings of Nietzsche, Heidegger, Arendt, Habermas, and others grow – has to do with what I call the four liabilities in Kant. These liabilities refer to how Kant is commonly read in Anglophone philosophy based on his central works, namely the Groundwork for the Metaphysics of Morals and the Critique of Pure Reason. The four include: a chauvinistic anthropocentrism, a maxim-centric nonconsequentialism, an individualism that precludes the consideration of long-term and global perspectives, and finally a dualistic separation of humanity from nature. A few innovative commentators have paved the way for this project and I am indebted to them. Toby Svoboda (Reference Svoboda2012) and my late advisor Martin Schönfeld are among these innovators. Yet Svoboda’s outline of a Kantian environmental ethic does not address the climate crisis, and Schönfeld’s contributions do so in a non-systematic fashion. Besides bridging environmental philosophy and Kant scholarship – to show that Kantians have something meaningful to say about the crisis and to defend Kant as no dead-end for environmental thinking – this book aims to present the most wide-ranging coverage of Kant’s texts and philosophical ideas presently available on this subject. I will say more on the comprehensive treatment of Kant’s ideas at the end of this chapter. First, it is important to motivate the project with a look at the state of the world, not of Königsberg, but of today.

I.1 The Climate Crisis and Philosophy

That climates change is no new concept. In fact, Kant himself writes about the natural shifting of climates in his Physical Geography and essays on earthquakes during the eighteenth century. He even opines that humans may cause climatic variations on small scales (GNVE 1:453, PG 9:177, 295–300). Yet it wasn’t until after Kant’s death and into the 1800s that scientists such as Jean-Baptiste Fourier and John Tyndall began to notice that atmospheric gases, heating, and ice ages were related (Garvey Reference Garvey2008, 17). In 1896, with Swedish scientist Svante Arrhenius, it became possible to understand the rudimentary mechanisms behind “greenhouse gas” emissions (so-dubbed by Fourier) and global heating. It is surprising to learn that Kant and others, only decades after him, speculated on the possibility for changing climates. Despite this, many today think that our understanding of climate change is a new piece of knowledge. It is not. Indeed, fifty years after Arrhenius’s calculations,

What’s the purpose of these historical reflections? After all, isn’t the present book on Kant’s philosophy rather than the history and science of climate change?

First, these historical remarks remind us of the contemporary continuity of Kant’s ideas discussed in this book – especially those on physical geography, theoretical philosophy, and natural science – with our understanding of climate change as a real phenomenon. This relates to knowledge, and we now know that the current global concentration of carbon dioxide in the atmosphere exceeds 420 parts per million (PPM).Footnote ⁷ For some context on the significance of this number, consider that only a decade ago, 350 PPM was the conservative suggestion for “minimizing the risk of getting into zones of uncertainty and crossing thresholds that could lead to major changes in regional climates, alter climate-dynamics patterns such as oceanic thermohaline circulation, or cause rapid sea level rise” (Folke Reference Folke, Assadourian and Prugh2013, 23–4). In 2013, carbon concentrations passed the 400 PPM threshold, which – even then – alarmed experts: “The chances of limiting global temperature increases to 2 degrees Celsius (3.6 degrees Fahrenheit) within this century are ‘swiftly diminishing,’ … This goal was endorsed by governments in 2010 as a ‘safe’ maximum to avoid the worst consequences” (Renner and Prugh Reference Renner, Prugh and Mastny2014). On some estimates, if deforestation continues with 550 PPM exceeded, we should expect an earth-system 2.7 degrees Celsius warmer than 1988 (Richardson et al. Reference Richardson, Steffen and Lucht2023), which would commit us to catastrophic global change impacting large-scale extinction, food production, freshwater availability, and more.Footnote ⁸ Although our knowledge of previous civil collapse is shaky, “Societal declines, collapses, migrations/resettlements, reorganizations, and cultural changes were often associated with severe regional droughts … all occurring within the relative stability of the narrow global Holocene temperature range of approximately ±1 °C” (Steffen et al. Reference Steffen, Rockström and Richardson2018). In moving beyond 1 degree of heating, we are on the path to ecological collapse (Read Reference Read2022).

Second, these reflections remind us that the climate crisis is a human-caused one. It is obvious that climatic variations have occurred in the past, but the key difference is the scale at which they are occurring. These swift changes (on geologic timescales) are attributable to human causes, just as industrialization bumped the earth-system out of the Little Ice Age during Kant’s life (Painter et al. Reference Painter, Mark, Kaser and Abdalati2013). The foremost authority on climate science, the Intergovernmental Panel on Climate Change (IPCC) releases key summaries of their findings, or Assessment Reports (ARs), which are the result of the consilience of thousands of peer reviewed articles spanning physical science to social science. As the sixth AR concludes, it is “unequivocal” that humans have warmed the atmosphere, ocean, and land, it is “virtually certain” that extreme weather events are its result, and 1.5 degrees of global heating is to be expected under the most likely scenario projections.Footnote ⁹ In short, the climate crisis is not only related to knowledge, but is related to humanity’s self-understanding as a global force (hence, the suggestion of “Anthropocene” as our new geologic epoch).

These reflections remind us that we have understood the causes of anthropogenic climate change for decades. We also know that those who have contributed the least to the crisis will undoubtedly suffer the most. This will be important to keep in mind when we think about individual responsibility for climate emissions in contrast with fossil fuel corporations who knowingly misled the public about the extent of their culpability (Supran, Rahmstorf, and Oreskes Reference Supran, Rahmstorf and Oreskes2023). Climate change is thus not only an epistemic challenge but an ethical one. In short, the crisis encompasses Kant’s four questions of philosophy, which concern knowledge, ethics, hope, and humanity (KrV A805/B833, Log 9:25).

Although the crisis beckons us to reflect anew on Kant’s four questions for the Anthropocene, it is, most importantly, an existential problem. Why is this? Climate change will involve, and presently involves, impacts such as extreme weather and resource shortage that harm humans and nonhumans alike. Graham Parkes summarizes the connection between climate change, climate impacts, and the existential challenge of humanity:

The impacts of the crisis do not only affect wealthy nations of the world indirectly, via climate refugees. They also affect them directly. It is therefore no mere future danger. To list just a few of these existential impacts, consider the AR6’s summary for policymakers:

If these impacts couldn’t get any worse, there are in addition perverse incentives at play. For example, as wealthy nations begin to adapt to climate emergencies, there will be less motivation and resources to mitigate emissions and slow the runaway climate train. Due to short-term tunnel vision, we will pass the buck with the worst climate excesses for the unborn (Gardiner Reference Gardiner2011).

What should we take away from this? First, addressing the climate crisis requires thinking broadly and collectively across space and time. Liberal individualism and an overemphasis on the short-term, as Rupert Read (Reference Read2022) argues, must be questioned. Luckily, philosophy provides the relevant tools for thinking about these in new ways. And, as Byron Williston (Reference Williston2021) and Graham Parkes (Reference Parkes2021) convincingly show, the philosophical canon can be one tool for doing so.Footnote ¹⁰ Second, the crisis is no mere scientific problem, nor a problem for engineers or economists. As Martin Schönfeld (Reference Marx and Tucker2016) reminds us, climate change is both a universal harm and a problem rooted in values. Fortunately again, philosophy excels in these domains. Philosophy involves reflection on values, even worldviews. Philosophy also excels in assisting us to think consistently and on large scales, both epistemically and ethically.Footnote ¹¹ Since philosophy thus matters for the crisis and since there has been a recent movement in the greening of the philosophical canon, especially vis-à-vis climate change, it makes sense to ask why one of the most influential philosophers has been neglected.

I.2 Why Kant?

I mentioned at the outset that this book fills two holes in the literature at the intersection of Kant scholarship and environmental philosophy. It’s a bit more complicated. In fact, there are actually three gaps in three different literatures. First, there is a gap in the applied literature on Kant. In both Kant scholarship and applied philosophy more generally, Kant’s philosophical views have been fruitfully applied to a wide range of contemporary topics including debates on healthcare, universal basic income, and artificial intelligence. These applications include global political topics too: nuclear war, interventionism, global poverty, and beyond.Footnote ¹² While applied philosophers have begun to broach the topic of Kant and environmental degradation, there is a curious lack of sustained engagement with his views and climate change, at least in the level of monographs, and this book aims to show that there is no good reason for this gap. At the same time, there is a new greening canon tendency in environmental ethics. Kant is curiously absent. Finally, since climate ethics has become its own autonomous field and is less wary of mobilizing anthropocentric views, it is surprising that Kant’s philosophy is also absent here. If the canon is mentioned, Rawls and other thinkers are favored in the literature (Rodeiro Reference Rodeiro2021). All three literatures reject Kant for the aforementioned reasons: In applied philosophy and climate ethics, Kant is seen as an interior-oriented nonconsequentialist, whose individualistic approach is insufficient for thinking globally and in the long term. In environmental philosophy, Kant is a dualist who elevates humanity above nature, and whose anthropocentrism therefore makes him more of an obstacle than a philosophical resource.

The present book brings together the three camps, making the case for Kant’s qualified inclusion. I say qualified, since this book will also remain critical of Kant’s own shortcomings, such as his racism and sexism. Despite these, it is worth taking the Kantian view seriously. Kant scholars have more to say about the environment and climate change than they may think, while environmental and climate philosophers have an unlikely ally. Some positions in environmental philosophy, specifically radically anti-anthropocentric ones, are easily rejected by laypersons and policymakers (Norton Reference Norton1991). At best, they are seen as too idealistic, and at worst they appear to conflict with common intuitions. Kant’s views have a unique advantage in being, in many cases, incredibly influential in our thinking about human rights, the rule of law, international law, aesthetics, and social science. In addition, Kant’s practical views are systematically defended, which allow for environmental and climate philosophers to avail themselves of robust forms of argumentation to support their policies. Deep ecology’s founder Arne Naess (Reference Naess, Drengson and Inoue1995) recognized the need for this too. Pragmatically speaking, then, it is unwise for environmental philosophers to marginalize Kant.

This book is not primarily a work in ethics or policy, though I will touch on these in due course. It rather presents a decidedly Kantian way for thinking about the climate crisis, drawing insights from a wide range of Kant’s works. When I speak of insights for non-Kantians, I am operating from assumptions about the convergence of enlightened anthropocentric views and non-anthropocentric views regarding policy. As a reminder, which Michel Bourban summarizes rather nicely, “Norton’s famous ‘convergence hypothesis’ relies on the idea that both an enlightened ethical anthropocentrism, supporting the moral superiority of humans to everything else in the natural order, and a consistent intrinsic value theory, such as biocentrism or ecocentrism, will have similar policy implications” (Norton Reference Norton1991, 237–43) (from Bourban 2022). While several of Kant’s views – such as his pre-critical philosophy of nature I explore in Chapter 3 – are not obviously anthropocentric, I stipulate that Bryan Norton (Reference Norton1991) got something right with his convergence hypothesis. I hope to show that many of the aims of environmental philosophers can be justified from a Kantian perspective, though they differ in forms of argumentation and values. Chapter 1, for instance, shows this regarding nonhuman animals. When he touches on Andrew Light’s practical pluralism, Michael C. Altman suggests, much like I will do, that “environmental ethicists should not reject Kant out of hand, but should adopt Kant’s position when it is useful to do so” (Altman Reference Altman2011, 63). Even if convergence is unlikely, my emphasis on the crisis should dispel some worries. After all, many environmentalist concerns are moot if we fail to address the crisis, with the sixth mass extinction being a case in point.

It is worth spending a moment to reflect on the title of the present work. While only Chapters 5–7 are specifically concerned with environmental obligations – and even there I do not feign to present a systematic account of Kantian sustainability duties – it seems appropriate to subtitle this work The Climate Crisis and the Imperative of Sustainability. First, this should remind the reader that, though primarily a study of the convergence between Kant studies and environmental philosophy with emphasis on climate change as an important proof-of-concept, this work also engages in normative debates in environmental ethics more broadly. Second, this subtitle is an homage to the important early thinker on the subject, namely Hans Jonas in his work The Imperative of Responsibility (Reference Jonas1984). Jonas was influenced by the very Kantian tradition explored in the present study, so much so that he criticized Kant’s categorical imperative in order to provide a provisional modification of it for sustainability.Footnote ¹³ While sustainability and climate change are conceptually distinct, and Jonas only wrote about the former, it is my hope to follow his lead in connecting sustainability to wider ethical concerns like the climate crisis. Climate change is, after all, a problem of us not living sustainably within the limits of planetary boundaries. Even more, Jonas was among the first to connect the dots between environment, technology, progress, and the human condition, which are now key topics in the environmental ethics and environmental philosophy literature more generally. Geoengineering is only one technological example we will touch on down the road. The reference to Heidegger’s student Jonas should therefore serve as a reminder to the reader of the green lineage of the Kantian tradition (indeed, Heidegger has also been subject to greenings, à la Rentmeester Reference Rentmeester2016). It thus makes sense to reassess Kant’s legacy in an age of human-caused climate change. This is especially important when that very legacy is accused guilty, at least in terms of justification, for the crisis in the first place.