Ancient Greco-Roman Views of Ecology, Sustainability, and Extinction: Aristotle, Stoicism, Pliny the Elder on Silphium, the Modern Legacy in Cuvier, Humboldt, Darwin, and beyond

Abstract

The ancient herb silphium is known as the first recorded species extinction, documented by Pliny the Elder in the first-century CE. Pliny, however, was an outlier among his peers; the predominant religious and scientific views of his time understood extinction as only local and/or temporary. Frameworks ranging from Aristotle to Stoicism understood ecology as occurring within a divinely natural order, whose broader realities humans could only influence in a limited way. We are therefore able to identify two distinct poles of Stoic scientific and religious thought around ecology: The first, drawing from Aristotle, sees nature as divinely providential and hierarchical, allowing for higher-order beings such as humans to freely extract from an self-replenishing environment; the second, with Pliny and others, understands nature more holistically and argues that humans’ ecological activity can be irreversibly destructive and should therefore be sustainable. We then explore how these two poles of thought extend all the way into the nineteenth century. There, a similar debate occurs in the views of Alexander von Humboldt, Charles Darwin, and Georges Cuvier, all foundational voices around the relationship between religion, science, and ecology that influentially shaped modern environmental views on humanity’s proper relationship to nature.

1. Introduction

While sustainability may be a relatively modern concept, attempts to understand the proper relationship between humanity and nature date back at least to ancient Rome and Greece. Unlike the modern world where science, religion, and philosophy tend to be discrete subjects with their own, distinct views on ecology, in the ancient Mediterranean these subjects were understood and studied together. As a result, ancient Greco-Roman thinking on sustainability and ecology was informed by a unique intersection of religion and science. For ancient Greek thinkers like Plato and Aristotle, for example, understandings of the natural world were part and parcel of a broader, philosophical exploration of both the nature of humanity and the nature of divinity. To understand whether nature was divine, for example, had important ramifications for understanding not only how nature operated scientifically but also how we should interact with other plant and animal species. For ancient Greco-Roman thinkers, the ethics of sustainability were inseparable from their metaphysics.

Ancient views on the metaphysical relationship between sustainability, ecology, religion, and science were not uniform, however. Key differences can be found not only in general metaphysical perspectives but specific views on ecology, such as around the notion of extinction. Some of our earliest thinkers such as Aristotle believed that extinction was impossible because creation was divinely ordained and largely outside the purview of human activity. But other thinkers, particularly from the school of philosophy Stoicism, diverged from Aristotle in understanding extinction as a terrible, irreversible event. In both cases, metaphysics similarly underpins views on sustainability, but different views on sustainability arise as a result of different metaphysical assumptions and understandings.

The same is true in modern thinking, from the Renaissance onward. In many ways, influential thinkers on modern ecology such as Alexander von Humboldt and Charles Darwin replicate the same debates around sustainability and ecology we find in ancient thought. Like the debates in Greco-Roman thought, key differences in metaphysical understandings of nature explain differing views on ecological topics such as extinction and humanity’s ethical obligation regarding sustainability. By exploring and comparing a variety of historical periods’ views on the intersection of sustainability, ecology, religion, and science, we can identify how our own metaphysical understandings and assumptions today can lead to a more ecologically sustainable future.

2. Ancient Greco-Roman views of religion, science, ecology, and extinction: Plato, Aristotle, and Theophrastus

In many ancient Greek and Roman traditions, it was believed that the natural world was created to provide for humankind. Humanity, as a higher-order lifeform, had natural dominion over all other organisms (e.g. plants and animals) and was thus fully warranted to utilize its authority for personal gain. As early as Homer’s Odyssey (8th century BCE), Odysseus’ encounter with the Cyclops Polyphemus sets up a clear contrast between civilized Greeks who cultivate and sow the Earth and the barbaric or inhuman Cyclopes who live in a state of wild, uncultivated nature [1, 2, 3]. Odysseus, in this view, was justified in his exploitation of the Cyclops and the violence done to him. Nature was not something peaceful to be respected but rather something to be conquered and used.

Ancient philosophical and scientific views reflected this same attitude regarding the hierarchical relationship of humanity to nature, starting with Plato (5th century BCE). Plato’s tripartite view of the self – reason, spirit, and appetite – held that while humanity shared its appetitive characteristics with other organisms such as animals, humanity was distinguished by its unique possession of reason which allowed the soul to ascend to a higher contemplative state [4]. Aristotle (4th century BCE) followed his teacher in emplacing humanity at the top of the creaturely hierarchy, and progressed even further by discussing in greater detail the relationship between humanity and nature. Underpinned by Plato’s ontological foundations, Aristotle’s view of the hierarchical relationship of humanity and/over nature became dominant and largely persisted in the western world – with exceptions, discussed below – until the European Renaissance.

Aristotle follows Plato by asserting that humanity is superior to nature on the basis of our rational character, which is not shared by other animals, much less plants or natural objects [5, 6, 7]. Aristotle understands this hierarchy teleologically, where everything in nature exists for a function – a notion that underpins many of his other scientific views too. This results in the conclusion that nature, and all of its many constituent parts lacking rationality, are subservient to rational humanity [8]. Aristotle famously and explicitly articulated this view in the Politics:

“In like manner we may infer that, after the birth of animals, plants exist for their sake, and that the other animals exist for the sake of man, the tame for use and food, the wild, if not all at least the greater part of them, for food, and for the provision of clothing and various instruments. Now if nature makes nothing incomplete, and nothing in vain, the inference must be that she has made all animals for the sake of man.” [9]

This view, of what is ultimately a divine and providential understanding of nature undergirded by an anthropocentric metaphysics, is widely present in both Peripatetic and Middle/Late Stoic thought (3rd century BCE – 3rd century CE). We will see many parallels in our treatment of Stoicism below.

Aristotle was aware of the fact that ecological exploitation could result in the decline of a wild species’ population, but also held the belief that the creation of life happens spontaneously and continuously, in a manner irrespective of human conduct [10]. In On the Generation of Animals (De Generatione Animalium, henceforth GA), Aristotle posited that the creation of an organism could occur by means of sexual reproduction but also due to spontaneous generation (GA 759a-b, 762a), a climactic process of admixture between rain and matter which we also see in Lucretius and Pausanias [11, 12]. This chthonic, spontaneous generation is present in a variety of species, for example, the fish that he discusses in History of Animals (HA) (HA 569a, 548a; cf. HA 539b). Such views were extended by later thinkers to a whole host of organisms, ranging from amphibians to mammals [13, 14].

Aristotle extends his naturalistic theories to metaphysics, as “the explanation of animal generation also has metaphysical importance for him … the generation of an entity must be explicable within that system” [15]. For Aristotle, all generation – spontaneous and not – depended not only on localized conditions (which might conceivably be influenced by humans) but more fundamentally on the metaphysical conditions of the cosmos more broadly, namely “the activity of the heavenly bodies upon the pneuma and the material” [15]. Humans, of course, affect the natural world, but the productive capacity of the natural world is an inevitable product of larger forces beyond the sphere of human influence. Aristotle’s view explains why the notion of extinction was largely foreign to him, for it violated the notion that humanity could have a permanently destructive effect on the environment or any single given species.

Theophrastus (4th-3rd century BCE), successor to Aristotle, articulated this view well: he claimed that the silphium plant came into existence as a result of “spontaneous generation” after a black rain of a “heavy, pitchy” nature blanketed the region of Cyrenaica (present-day northeastern Libya) in the 7th century BCE [16]. Here, Theophrastus mirrors the broadly providential view of nature that Aristotle held: the loss of any one plant or animal species was only temporary and humanity’s influence on the environment marginal. After all, any species whose population had been diminished by human activity could spontaneously reappear at any moment. Extinction in the modern, permanent sense of the word was simply impossible according to Aristotle’s (dominant and highly influential) scientific and metaphysical views.

3. Pliny the elder: a new voice in ecology

One figure stands apart from this Aristotelian strand of thought: Pliny the Elder. Pliny (23–74 CE) was a highly distinguished member of ancient Roman society. Over his life he held important military positions and was closely connected with the political elite, for example a direct friendship with Vespasian [17]. He was also prolific in his literary output, which included not only historical works but also extensive work in the natural sciences [18]. Most notable in the latter was his Natural History (Naturalis Historia), a sprawling and encyclopedic work with huge swaths of material in the natural sciences including geography and botany.

Pliny’s work contains many prior influences from Aristotle and subsequent philosophical traditions [19]. In fact, his Natural History is full of references to both the idea of spontaneous generation by nature and the notion of nature being hierarchical and therefore of use to humanity. On the latter, in a typical example, he writes that “[Nature] pours forth a profusion of medicinal plants, and is always producing something for the use of man.” (1.2.63) [14].

Pliny also follows Aristotle in the importance granted to the spontaneously generative power of wind and rain. He variously describes reports of matter falling from the sky, ranging from the mundane (stones; tiles) to the alarming (milk; blood). While the former might be explained away by the wind taking up material objects, the latter is not explained but merely highlighted as a given (1.2.38, 57) [14]. Pliny even notes the generation of plants in this manner, reiterating Theophrastus’ account of silphium’s appearance as an example (3.16.61) [14]. He concludes broadly that “All these productions owe their origin to rain, and by rain is silphium produced”, right in line with Aristotle (4.22.48) [14]. However, in nearly every such instance, Pliny provides details such as the location and date, perhaps to suggest that he himself is skeptical and that the reader should go confirm the occurrence of these events for themselves.

Importantly, Pliny expands this conclusion with a claim that notably departs from the prevailing ecological theory of his predecessors: “As already observed, the silphium of Cyrenae no longer exists” (4.22.48) [14]. Indeed, it is in Natural History that we find, for the first time in ancient western history, an explicit engagement with the notion of extinction as a permanent ecological phenomenon, with regard to the ancient herb silphium [20]. Noting a variety of the distinct geographic, botanical, and cultural factors at work, Pliny comes to the novel conclusion that the actions of humanity directly resulted in the extinction of a species and that this result is irreversible; recent research has argued that human-caused climate change was the principal factor in silphium’s extinction [21].

This conclusion begs a series of questions around ancient ecology and religion. If Pliny believed that the natural world providentially furnished things for humanity, what would it mean that one could no longer exist? How could the extinction of a species be permanent if that same species were the product of natural forces such as wind and rain? If humanity has little power over these divine and natural forces, how could we even force something to go extinct if we tried?

We argue that the key to answering these questions can be found in Pliny’s metaphysics, in particular at the intersection of religion and ecology. This intersection reflects a particular brand of Stoic thinking that highlights a fundamental tension in Stoic thought around the role of humanity and its relationship to a divinely understood nature.

Pliny’s metaphysics take influence from both Aristotelian and prior Stoic views (among others) that there is a power beyond humanity over which we have little control. Pliny clearly conceives of nature in the classic Stoic sense as divine, not in a deistic sense of an agential and person-like god, but rather in a broader and more abstract sense of the divine. He asserts that the “world, and whatever that be which we otherwise call the heavens … we must conceive to be a deity, to be eternal, without bounds, neither created, nor subject, at any time, to destruction.” (1.2.1) [14] As such, he asserts that “it is ridiculous to suppose that the great head of all things, whatever it be, pays any regard to human affairs” (1.2.5) [14]. It is clear that nature, in the sense of ecology, is understood as itself a divine force: “the power of nature is clearly proved and is shown to be what we call god” (1.2.5) [14]. In this paradigm, nature cares little for humans because we are merely small creatures living within the grand operations of the cosmos; therefore nothing we do can truly influence nature. Such a line of thought largely underpins Aristotelian and some Stoic views, leading to the notion that it is not possible for human actions to cause the extinction of a species.

Pliny, however, comes to a different conclusion. Although he clearly understands nature as a divinity, he does not view nature as an agential and a person-like god. Nature, therefore, cannot operate according to whims, desires, and intentions; in other words, not like the gods classically understood in Greek mythology. Rather, the divinity of nature operates according to universal principles, such as those of science:

“[God cannot] make mortals immortal, or recall to life those who are dead; nor can he effect, that he who has once lived shall not have lived, or that he who has enjoyed honours shall not have enjoyed them; nor has he any influence over past events but to cause them to be forgotten. And, if we illustrate the nature of our connection with god by a less serious argument, he cannot make twice ten not to be twenty, and many other things of this kind.” (1.2.5) [14]

Nature, as with god, cannot bring somebody back to life or change the past or any number of other things. Nature is limited by nature’s own inherent operations.

This point helps explain Pliny’s earlier comments around humanity’s inability to create, destroy or otherwise alter the natural world. When Pliny states that humanity cannot affect nature (which is framed as a god), he is asserting that humanity cannot change the fundamental workings (e.g. natural operations; universal laws) of the universe. These not only include the known processes of the natural world (e.g. gravity, geology, reproduction, chemical and biological change, etc.) but also the unfounded natural processes which Pliny believed to have existed (e.g. spontaneous generation of organisms and material objects). In stating this, Pliny is not asserting that humanity cannot influence the manifestation of nature on Earth. So while humans cannot change the inherent ability of two animals to reproduce, for example, they might capture, injure, or kill the animals and thereby thwart the manifestation of this biological process. While humans cannot change the properties of water such that it turns to steam at high temperatures and freezes at low temperatures, humans can surely remove or add heat to water to prevent or facilitate these changes in a given situation. The causes and operations of nature/god remain beyond the bounds of humanity, but not the effects and manifestations. To briefly look ahead, Charles Darwin himself settles on such a view too.

Pliny’s differentiation (causes/operations vs. effects/manifestations) is crucial, as it allows him to take a wider view on the deleterious effects of human actions on the natural world. In poetic language strikingly similar to modern ecological writing, Pliny takes a dark view of humanity’s ecological behaviors:

“[Nature] is continually tortured for her iron, her timber, stone, fire, corn and is even much more subservient to our luxuries than to our mere support. What indeed she endures on her surface might be tolerated, but we penetrate also into her bowels, digging out the veins of gold and silver, and the ores of copper and lead; we also search for gems and certain small pebbles, driving our trenches to a great depth. We tear out her entrails in order to extract gems with which we may load our fingers ... And truly we wonder that this same Earth should have produced anything noxious!” (1.2.63) [14]

Nature is readily anthropomorphized, in a prototypical blend of religion and ecology, as Pliny notes that the natural ecological balance theorized by prior thinkers was about meeting natural needs. By contrast, humanity’s avarice for “luxuries” beyond “mere support” leads to nature being “continually tortured”, being penetrated for mineral extraction, and having her entrails torn out sheerly for the sake of human decoration.

Along similar lines, Pliny affords nature some broad agency, using the extractive relationship of humanity and nature to explain why the “Earth should have produced anything noxious”. Humanity, it seems, has upset the divine and natural order, with resulting consequences. In another strong echo of modern ecological writing, Pliny then continues to say that all of this exploitation of the natural world would result in disastrous consequences for humanity, “inasmuch as all this wealth ends in crimes, slaughter, and war” (1.2.63) [14]. By upsetting the divine and natural order, in the end we are only hurting ourselves. And nature – well, she will exist long after we are gone: “while we drench her with our blood, we cover her with our unburied bones; and being covered with these … her anger being thus appeased” (1.2.63) [14]. Nature is both divinely anthropomorphized and understood as unified with the human condition; in doing the Earth wrong we do ourselves wrong as we are part of nature; and ultimately this is all understood not only in a clear scientific context of cause and effect between the natural and human worlds but also in the urgent terms of a sincerely held religious view of our place in the cosmos.

4. Two poles of stoic thought: a divergence around humanity’s role in ecology: hierarchy and extraction versus holism and equilibrium

Pliny’s views are strikingly written, novel with regard to the recognition of extinction, and distinct in their ability to link together religion and ecology in a way that finds parallels in the modern world. Indeed, we will treat the latter parallels explicitly in our next section. But in the context of ancient Greco-Roman views around religion and ecology, Pliny’s views highlight an interesting tension in the predominant religion-ecology nexus of the day, as found in ancient Stoicism.

Philosophically, Pliny is probably aligned closer to Stoicism than any other philosophy. We must caution that he was not a systematic and whole-hearted Stoic through and through [22]. But particularly his natural philosophy, that intersection between ecology and religion, was clearly and most strongly informed by Stoicism [23]. Sometimes specific aspects of his thought can even be traced with confidence to certain Stoic thinkers [24]. More broadly, he was not only familiar with foundational ideas from Stoicism and key texts and thinkers such as Zeno (4th-3rd century BCE, founder of Stoicism) [23], but also a variety of other philosophers from whom he freely drew [25]. So while we focus here on Pliny’s Stoicism in light of other Stoic thought, it is important to remember that Pliny’s use of ancient philosophy was not confined to Stoicism alone.

In Stoicism, however, there were notable differences of thought, with debate around subjects such as cosmology, ethics, and human nature. Despite core, shared ideas across different thinkers, Stoicism was no monolithic system of thought and it contains both disagreements between thinkers and changes over time and. We argue that one of these internal Stoic debates which has not yet been fully recognized or explored is the relationship of humanity to nature. In the language of our conclusions above regarding Pliny, Stoic thinkers varied in how they understood the relationship of religion and ecology.

We identify two general poles in Stoicism around the relationship of religion and ecology. One pole, which we have already explored above, generally follows the Platonic and Aristotelian view: Humanity was created as a higher order being in a hierarchically ordered universe, and it is therefore natural and in some sense good for humanity to make use of and even dominate the natural environment.

Stoic thought roughly contemporaneous to Pliny, in the first and second centuries CE, is full of these ideas, ranging from Epictetus to Seneca the Younger to Marcus Aurelius. Perhaps most famously, Marcus (2nd century CE, a century after Pliny) wrote in his Meditations that the “lower exists for the sake of the higher” (11.18) [26]. For Marcus, lower order forms were created providentially and according to some type of divine plan; it was therefore normal and necessary for higher order forms to make use of them. This was not only a statement about religion and ecology, but also a convenient political ideology for Marcus (one of the most relentlessly imperial emperors), who could use this Stoic ideology to help justify his campaigns against militarily weaker peoples; we see a similar link between (holistic) ecology and (equitable) politics found in the modern period in Alexander von Humboldt, discussed below.

More proximately to Pliny, meanwhile, we find similar ideas expressed by Epictetus and Seneca. Epictetus, in his Discourses compiled by his pupil Arrian in the early first century CE, writes:

“For animals not being made for themselves, but for service, it was not fit for them to be made so as to need other things ... Nature has formed the animals which are made for service, all ready, prepared, and requiring no further care. So one little boy with only a stick drives the cattle.” [27]

Such a view aligns easily not only with Marcus and some of Pliny’s comments but also the ecological-hierarchy view of Aristotle. Nature has some things ready made for others and humans are rightly in charge over cattle; hierarchy and the ruling of one organism over the other is natural and even good.

This notion of some organisms being naturally created for service to others finds clear parallel in Stoic views of the body. This is best espoused by Seneca the Younger (1st century CE), who writes:

“I think that the Earth is controlled by nature, and on the model of our own bodies, in which there are both veins and arteries; the former are receptacles for blood, the latter for breath. In the Earth too, there are some passages through which water runs, others through which breath does; and nature has created such a resemblance to the human body …” (3.15.1) [28]

The body makes for a ready parallel to nature, the micro in the macro, as individual elements of the body are created for and function in service to the whole. One would readily cut off a finger to save an entire organism, and as such there are clearly aspects of the body which are subservient to the whole and therefore relatively expendable.

Extending this view to a macro, cosmic scale, this metaphysical and religious view of our place in the universe underpins Stoic ethics, in particular the view that suffering and death are ultimately inconsequential. A single human life is to the universe as, perhaps, a fingernail is to an individual human. Just as the universe might see fit in its grand operations to destroy us individually or as a species, so too we should think nothing of cutting off and discarding a fingernail. In both cases these operations are natural and, in that Stoic sense, good. By the same logic, some organisms higher in the grand hierarchy of nature can and even should make use of others.

There is a second pole of Stoic thought, however, that speaks to how humanity should not simply exploit and extract and dominate, but rather exercise our reason to live in harmony. This view is also, in fact, derived partly from Platonic and Aristotelian views privileging the rational mind of humanity. Yet instead of seeing humans at the top of a hierarchy and justifying domination, our place at the top of the created hierarchy results from reason, which – when properly exercised according to Stoic principles – results not in violence but in harmony. Thus, Epictetus can write the following too:

“Well then God constitutes every animal, one to be eaten, another to serve for agriculture, another to supply cheese, and another for some like use; for which purposes what need is there to understand appearances and to be able to distinguish them? But God has introduced man to be a spectator of God and of his works; and not only a spectator of them, but an interpreter. For this reason it is shameful for man to begin and to end where irrational animals do; but rather he ought to begin where they begin, and to end where nature ends in us; and nature ends in contemplation and understanding, and in a way of life conformable to nature.” (ch. 6) [27]

While the first part of this passage seems to reflect the more extractive, dominating view seen in our first pole of Stoic thought, here the conclusion is notably different. It is indeed “shameful” for humans to do what animals do, presumably fight, suffer, and struggle over narrow and instinctual concerns. Instead, humanity’s rational nature calls us to a higher purpose as our “nature ends in contemplation and understanding”, an echo of Platonic influence. Conforming to nature does not simply involve participating in a violent, exploitative hierarchy of being, but rather this “life conformable with nature” is one that is aware of, and attentive to, one’s effects on others. ‘Conforming’ denotes adaptation and accommodation, not bending others to one’s own will, whim, or preference.

We see this second, accommodating pole of Stoic ecological thinking voiced severally by Seneca. Seneca writes that the proper operation of nature has to do with the notion of sufficiency:

“All things by nature seize enough for their own nourishment, and the world has appropriated as much as it needed for eternity. I shall offer you a tiny illustration of this important fact: eggs contain enough liquid to generate the creature that will emerge.” (2.5.2) [28]

The proper functioning of nature manifests an ecology in a state of equilibrium. Of course, some things naturally make use of other things (the creature in the egg and the liquid within), which well matches the first pole of Stoic thought, but this ‘making use’ reflects only the particular amount that the Earth needs. This amount is tremendous, sufficing forever, but only insofar as organisms within a species exist and behave according to their natural needs; so is the case of the chick emerging from the egg. The egg provides liquid for emergence, the natural need, but nothing more that might reflect preference, desire, or (in human terms) greed.

Indeed, Seneca understands the world in terms of a balanced reciprocity according to natural need and consequent use:

“Nothing is exhausted if it returns to itself. There are reciprocal exchanges between all the elements: whatever one loses turns into another, and nature weighs its parts as if they were placed on a pair of scales, to make sure that the world does not become unbalanced because the equality of its components is disturbed.” (3.10.3) [28]

Nature operates in a balance and the natural operation of its parts maintain that balance. If humans take a natural amount – such as for their natural “nourishment” per the earlier quote above – then the Earth will reciprocally take and in turn provide this nourishment. However, moving beyond what is natural – to take more than what is necessary for mere nourishment – will upset this balance:

“Any deviation by nature from the present state of affairs is sufficient for the destruction of mortals. So when that inevitable moment arrives, fate sets in motion many causes at once; for such a change cannot occur without the world being shaken.” (3.27.3) [28]

Nature provides if its constituent parts behave accordingly. If the parts do not behave according to their nature (e.g., nourishment alone) then what follows is inevitably “destruction”. Crucially, this destruction will occur via violence amid the world itself (“such a change cannot occur without the world being shaken”). Deviations from nature will invite consequences that will convulse the world and punish humanity as a result, for indeed we are a part of nature. To continue our body analogy from earlier, if a finger ceases to operate properly by harming the body, it will be subject to inevitable destruction. This destruction will harm the greater whole (body = nature) but will certainly punish the offending part (= organism/species).

This line of metaphysical thinking aligning religion and ecology readily reflects widely held Stoic understandings of ethics. In Stoicism, one should behave according to one’s general nature as a species (which Stoics call ‘a good’) and even according to one’s individual desires (which Stoics label a ‘preferred indifferent’, being neither good nor bad). A human can therefore be justified in using violence to defend their life because of an organism’s basic biological rights and nature directed toward survival, but not justified in using violence simply to get what one desires.

Indeed, Stoic ethics generally do not espouse violence but rather acquiescence; not domination but rather peaceful differences; and not extraction for excess but rather making do with the bare minimum. This is not only a metaphysical view about the ideal ‘Stoic sage’ and our relationship to the cosmos but also has clear applications to our micro-cosmos too, namely our ecological environment. Just as Stoics argued we should generally accept our lot in life and seek no more than demanded by nature for sufficiency, by extension so too should we use nature and other organisms where necessary but never to a point of excess. One must eat, but never feast; one must kill to survive, but never for sport; one might need to extract resources to build a house to survive the winter, but this does not mean one is justified in extracting resources for ornamentation.

Furthermore, deviating beyond what is necessary for mere “nourishment”, to again use Seneca’s term, is ultimately a recipe for destruction. Firstly, it results in the forfeit of one’s individual virtue and thereby doing oneself violence – Stoics label as ‘bad’ anything that undermines virtue. But secondly, it also harms the wider environment (nature/god itself) which in the Stoic metaphysical and religious view is ultimately aligned with the self, just as the finger is identified with the body but should never be privileged before it. Any wider damaging of nature/god disturbs natural order, and this disturbance is not only bad for nature/god (a metaphysical and religious ill) but will also ultimately result in partial or complete self-destruction. For this line of Stoic thinking, ecology is religion and therefore sustainability constitutes proper ethics.

5. The legacy of ancient ecology and religion in modern thought: Parallels between ancient stoicism and Humboldt, Darwin, Cuvier, and modern conservationism

The ancient extinction of silphium seems to reflect the second pole of Stoic thought that we have detailed here. The harvesting and use of silphium was natural and normal, and in that sense good, as part of our biological existence on this Earth. But over-harvesting beyond what was necessary for nourishment showed improper judgment, both about ourselves and the natural world. Because we can affect the manifestations of natural processes, humanity has the ability to disturb the balance of nature itself. By disturbing this balance, we act not only non-virtuously from the Stoic perspective but also actively damage nature/god which will, in turn, have damaging consequences for us.

From an ecological point of view, certainly the first consequence – that we sacrifice our own virtue when we take more than is necessary – has continued to bear out time and again over the course of human history. A philosophical orientation toward nature of unfettered use and extraction beyond the survivalist minimum has resulted in cultural attitudes of extraction, imperialism, and a host of hierarchical and bigoted views ranging from neo-colonialism to outright racism. A capitalist ideology of profit maximization for personal gain will doubtless incentivize productivity and capital production, but at the cost of disincentivizing a virtuous relationship, not only with nature but with each other too.

The second ecological consequence is even more obvious: an attitude of not living in ecological balance and self-sufficiency has resulted in an unprecedented rate of species extinction, both plant and animal [29, 30]. The so-called ‘Anthropocene Epoch’ has been so devastating to other biological life on Earth that this era of human dominance has been rightly faulted for “the sixth mass extinction” [31]. Pliny’s Stoicism, which recognized that humans can destructively influence nature to the point of making a plant go extinct, was simply the beginning. To this we can add the many ways that, as Stoics predicted, the Earth has responded with violence to both itself (“the world being shaken”) and humanity (“destruction”): anthropogenic climate change and hazardous pollution are the two most ready examples that come to mind, to say nothing of the warlike destruction our species visits upon itself with historical regularity.

Modern ecological thinking has attempted to redress our relationship with the natural world in a manner strikingly similar to ancient Stoicism, by re-thinking nature and our place in it in metaphysical and religious terms. In ancient Stoicism, Seneca described a view of nature that emplaces humanity within the framework of religious humility, as he is baffled by humanity’s narrow-mindedness around our place within nature while being simultaneously in awe of nature and its grand operations. These two operate side by side:

“I myself give thanks to nature whenever I see her, not in her public aspect, but when I have entered her more remote regions, when I am learning what the material of the universe is, who is its creator or guardian, what God is, whether he is totally focused on himself or sometimes takes notice of us too, whether he creates something every day or has created once and for all, whether he is part of the world or the world itself, whether even today he may make decisions and amend part of the law of fate, or whether it would be an impairment of his greatness and an admission of error to have made something that needed alteration.” (1.3) [28]

Seneca continues, framing the issue truly as a matter of good and evil, extending the religious view of ecology in the previous quote:

“[The mind] has consummated and fulfilled the blessings of human destiny only when it had trampled over every evil and has sought the heights and entered the inner recesses of nature. Then, as it wanders among the stars themselves, it takes delight in laughing at the paved floors of the wealthy and at the whole Earth with its gold – I refer not just to what it has disgorged and given to the mint for stamping into coinage, but also to what it keeps hidden for the greed of posterity.” (1.7.8) [28]

Humans have moved far beyond nourishment and, in Stoic terms, have acted non-virtuously, extracting not out of necessity but out of greed. This is all fundamentally baffling, for our desires and wants and wars are miniscule in a metaphysical view that blends nature with god:

“The mind cannot despise colonnades, and ceilings gleaming with ivory, and topiary forests and rivers channeled into houses until it has toured the entire world and until, looking down from on high at the Earth – tiny, predominantly covered by sea, and, even when it rises above it, mainly uncultivated, and either burnt or frozen – it has said to itself, ‘this is that pinprick that is carved up among so many nations by sword and fire?’” (1.7.8) [28]

Such views are striking, not only in their poetry but in their similarity to modern ecological writings, especially those with a more religious, spiritual, or new-age bent. The origins of modern environmentalism and ecology can be rightly traced to the work of Alexander von Humboldt (1769–1859), the famous naturalist, explorer, and polymath whose influence in the world of nature science was so colossal and unparalleled it is difficult to overstate [32].

Among Humboldt’s many scientific contributions, one of his most lasting was the view of nature as a unified whole governed by inter-relationships, personified in his magnum opus Kosmos where he argued for the interrelationship of not only all of biological nature but all of science and humanity too [32]. As far as historical influence, Humboldt’s views and writing importantly gave rise to Charles Darwin’s (1809–1882) own views on evolution and speciation, who in turn has become much better remembered than Humboldt himself. But Humboldt’s work was one of only two that Darwin brought on his famous voyage on the Beagle to the Galapagos Islands and beyond, and Darwin’s writings engage extensively with Humboldt, whom he admired greatly [32].

In a fascinating parallel to the two poles of ecological thinking we found in ancient Stoicism, we see a similar dynamic playing out in the work of Humboldt and Darwin around their views of nature. Scientifically, Humboldt and Darwin are rightly understood as part of a single intellectual lineage, for they both understood nature as acting upon and within itself, and as both highlighting the importance of understanding nature holistically in terms of the inter-relationship of all its parts, ranging from climate to population dynamics to the dynamism of natural change.

But there is a core difference between the two in terms of how they understood nature’s holism [33]. Humboldt took the much broader view, that nature can and should be understood holistically, that ecology in the large was to be understood as a single organism functioning in harmonious equilibrium. By contrast, Darwin focused on the notion of competition (so-called ‘survival of the fittest’), that nature was teeming with violence and the struggle for resources. In the words of Stephen Jay Gould, there are (at least) three fundamental “aspects of the new Darwinian world. All confute central aspects of Humboldt’s vision” [33]. First, Darwin believed that “Nature is a scene of competition and struggle, not higher harmony” as Humboldt believed [33]. Second, also contra Humboldt, Darwin argued that “Evolutionary lineages have no intrinsic direction toward higher states or greater unification. Natural selection is only a process of local adaptation” [33]. And third, Darwin concluded that “Evolutionary changes are not propelled by an internal and harmonious force”, which departed strikingly from Humboldt’s own conclusions [33].

Darwin understood nature locally and brutally, with a series of random, weighted events propelling survival and speciation outcomes. Humboldt saw nature broadly and beautifully, with a sort of divine order and harmonious outcome of balance. Of course, both are true biologically, as it is simply a matter of scale: at the micro level of individual organisms and species you see savage and unrelenting violence and competition; at the macro level of an entire ecosystem, however, one sees harmony, balance, and beauty. It merely depends on one’s own metaphysical view of where to locate the truth of nature.

Humboldt was himself not religious. Indeed, he does not mention God once in his magnum opus Kosmos, which described the entirety of the universe at both macroscopic and microscopic scale [34]. But his more spiritual perspective on nature is strikingly similar to the non-deistic view of ‘nature as god’ propounded by the Stoics, who frequently used the term ‘god’ in their writings but not in the sense of the person-like, agential deities found in Greco-Roman mythology. In both Humboldt and Stoic thinking, nature operates broadly and harmoniously and provides propitiously for all biological organisms. To pick up our argument from our analysis of the ancient sources, Humboldt’s view is closer to the second pole of Stoic ecological thought, which focused on balance and harmony and humanity’s ability to destroy and disrupt nature. Indeed, Humboldt’s works were innovative and influential in speaking to the deleterious human effects on nature, in some of our first theorization around species loss and climate change [32].

Humboldt’s more spiritual perspective on nature therefore lent itself to later ecological thinking along these lines. He was particularly influential, for instance, on the scientific (and sometimes even religious) views of later ecologists in the West. This includes both more historically proximate writers such as Henry David Thoreau (1817–1862, a founder of modern naturalism) and Ralph Waldo Emerson (1803–1882, leader of transcendentalism), but also later preservationists such as John Muir (1838–1914, the key driver for the founding of the National Parks System in the United States, which in turn became a model for the global West) and Rachel Carson, whose 1962 book Silent Spring in many ways birthed the modern ecological conservation movement [32].

Humboldt’s view also gave rise to analogical thinking in the humanistic and political sphere. He thought, for example, that because all of nature was unified and beautiful in its diversity, that such principles extended to human culture as well. He was therefore a strong proponent of cultural and racial equality, arguing loudly and across his entire life against slavery and in favor of equal rights to those oppressed by the European colonial empires [32]. For Humboldt, colonialism and theories of racial hierarchy were environmentally destructive too [32], showing the fundamental linkages between all of nature, not just plants and animals but humanity and human systems of politics too.

By contrast, Darwin’s view – of competition, violence, and hierarchy – well parallels the first pole of Stoic ecological thinking, that such principles are natural and normal in nature. The founders of modern naturalism and ecology, in other words, continued to struggle with the same tension we see in Stoicism. And while Humboldt made no mention of God in Kosmos, Darwin’s ecology more explicitly engaged with the notion:

“To my mind, it [nature’s perfection] accords better with what we know of the laws impressed on matter by the Creator, that the production and extinction of the past and present inhabitants of the world should have been due to secondary causes, like those determining the birth and death of the individual.” (383) [35]

In the words of a modern interpreter of Darwin, “Darwin invokes the “Creator,” but leaves him out of the work of life and death … The Creator may impress his laws on matter, but the laws of matter are all that are revealed by the phenomena Darwin investigates” (xxv) [35]. Like Humboldt, Darwin’s thought includes the “absence of divine intention” (xxv) [35], but while Humboldt is comfortable excluding deism entirely, Darwin is still willing to engage with the notion of a Creator. Humboldt’s religious views seemed to abstract away entirely from a creator god in terms of his ecological metaphysics; Darwin seemed to allow for a creator god but, in a manner strikingly similar to our second pole of Stoic thought, Darwin believed that divinity could be found in the metaphysical and scientific principles of nature while things like extinction were due to “secondary causes” such as human influence.

Darwin’s thought, meanwhile, gave rise to a very different kind of humanistic and political thinking from Humboldt’s. While Darwin himself was no racist or bigot and indeed was explicitly anti-slavery [36, 37], the notion of ‘Social Darwinism’ was later derived from his thought [38]. This idea – that hierarchy is natural and normal and thus such principles should also apply to human society – was used for decades in an attempt to justify slavery, racial hierarchy, and colonialism. Just as with Humboldt, we see that one’s metaphysical views of nature are extended into the world of politics and culture too. One might well favor Darwin’s biological perspective, and indeed there is a reason that we remember his name more than Humboldt’s when it comes to his theories of nature and its operations, but Humboldt’s more spiritualist view of metaphysical unity certainly leads to a more sustainable, holistic, and equitable view of human diversity.

We can now return to the idea that began our paper, extinction, and the role of scientific and religious thinking in its understanding. Our modern understanding of extinction stems from the work of Georges Cuvier (1769–1832), a contemporary of Humboldt whose scientific ideas cohere in some ways with the shared Humboldtian and Darwinian ecological frameworks. In Cuvier’s Essay on the Theory of the Earth (1813), he set out with the simple objective to determine the identities of organisms found in the fossil record [39]. Cuvier came to a bold conclusion: some of the fossilized animal remains found below the surface of the Earth were so unlike existing species that they must have gone extinct. Such a conclusion was controversial in his time. Other naturalists, such as Jean-Baptiste Lamarck (1744–1829), believed that species could not go extinct, but rather adapted to their environments throughout their lifetimes, ultimately passing on those newly acquired traits to their offspring [40, 41]. In this view, such fossils merely represented earlier versions of still-existing species, making extinction an impossibility.

Cuvier took the opposite view, arguing in favor of extinction and firmly opposing the idea of species adaptation:

“Why may not the presently existing races of land quadrupeds, it has been asked, be modifications of those ancient races which we find in a fossil state; which modifications may have been produced by local circumstances and change of climate; and carried to the extreme difference which they now present, during a long succession of ages? This objection must appear strong to those especially who believe in the possibility of indefinite alteration of forms in organized bodies; and who think that, during a succession of ages, and by repeated changes of habitudes, all the species might be changed into one another, or might result from a single species. Yet to these persons an answer may be given from their own system. If the species have changed by degrees, we ought to find traces of these gradual modifications. Thus, between the palaeotheria and our present species, we should be able to discover some intermediate forms; and yet no such discovery has ever been made.” [42]

Here, Cuvier proposed a revolutionary idea for his time: animal remains found in the fossil record offered clear evidence for species extinction. Yet in the same stubborn breath, he perhaps made the biggest blunder of his academic career by dismissing Lamarck’s idea that species could adapt to changing environments. In hindsight, we know that neither Lamarck nor Cuvier were entirely correct, but each of them had made an important contribution to the broader understanding of life on Earth.

Cuvier believed that all species were perfectly adapted to their environments and as a result, any significant change of those environments could threaten their very existence. This idea aligns closely with the Humboldtian view of nature’s harmonious balance of interrelated species, each of which occupies a unique ecological niche to the benefit of the larger whole. However, Cuvier did not always see nature as beautiful, but rather as a brutal system plagued by shocking changes, intense competition, and occasional catastrophes. This view – which parallels Seneca’s previous assertion that disturbing the balance of nature would result in its destruction – influenced Darwin’s own ideas about competition, ecological change, and extinction. Extinction, according to Darwin, only occurs when a species is unable to adapt to their changing environment.

Cuvier’s outright dismissal of species adaptation was in effect an intellectual roadblock, preventing him from capturing the whole picture of natural selection. In doing so, he also left open the major question of how species are created, lending credence to the ancient ideas of spontaneous generation and godly creation. Indeed, Cuvier’s own stance was widely used by creationists and those seeing divine design in nature [43], a position that has persisted in small and non-scientific areas of thinking today.

6. Conclusion: the metaphysics of ecology

In this chapter, we have surveyed key strands of thought in the western tradition, both ancient and modern, around the relationship between religion, science, ecology, and sustainability. In the ancient Mediterranean, the most influential explorations of this relationship include Aristotle and the later Stoic tradition. Our earliest views in ancient Greece saw nature as providential, divine, and therefore not allowing for human-caused extinction such as those of plants or animals. Later Stoic views, in particularly Pliny the Elder, noted the extinction of the famous and valuable plant silphium.

This extinction event illuminates a key difference between ancient Stoic thinkers. While Stoicism generally holds to a metaphysical view of nature as divine, Stoics themselves differentiated on the extent to which humans can and should exploit nature and its resources. We identified two poles of thinking in ancient thought: one pole that followed Aristotle in arguing that nature’s divine providence results in hierarchical exploitation being natural and therefore to some extent good; and another pole that departed from Aristotle, especially as articulated by Pliny, in arguing that nature’s divine providence results in hierarchical exploitation being unnatural and therefore to some extent bad. This difference results, we think, from the core metaphysical orientations of these two poles, regarding the nature of religion and ecology. The former pole sees sustainability outside the province of humanity, while the latter pole sees sustainability as a crucial element of one’s proper religious and philosophical orientation to the universe.

In the later west, we see this same metaphysical intersection, encompassing all of science and philosophy and religion around the subject of ecology, in the pioneering work of Alexander von Humboldt and Charles Darwin. Although aligned in a great many ways, Humboldt and Darwin departed in crucial ways around the nature of ecology. Humboldt’s metaphysical views of the cosmos see unity and harmony as fundamental principles, and therefore that human’s extractive behaviors are abnormal and morally wrong, going against the very principles of the universe. It is for this reason that Humboldt’s thought had an outsize effect on later syntheses of ecology, philosophy, religion, and sustainability, ranging from transcendentalism to modern eco-spiritualists. Such lines of thought in Humboldt and subsequent thinkers in his lineage well parallel the second pole of Stoic thinking, as found in Pliny but also in others such as Seneca and Epictetus, that views humanity as potentially destructive of nature’s natural and divine harmony. In this view, extinction is unnatural and fundamentally bad; humanity’s influence has resulted in a host of deleterious extinctions.

Darwin, by contrast, viewed competition and struggle as fundamental principles of nature. While Darwin did not pursue the humanistic social and political implications of his thought as Humboldt did, this metaphysical stance was appropriated by later thinkers who believed that the hierarchy and violence found in natural were natural and therefore good, using this stance to justify deplorable political, economic, and social systems. In this way, mutatis mutandis, such lines of Darwinian thought parallel the other pole of Stoic thinking, as found in the notorious imperialist Marcus Aurelius as well as the earlier Aristotle and his view of ‘natural slavery’ (Politics 1254b16–23) [44], that views humanity as deserving of nature’s bounty and that lower order beings of all kinds are naturally suited to be used by others. In this view, extinction is natural and not necessarily bad; indeed, extinctions and major extinction events have occurred long before the influence of humans.

An attention to both ancient and modern thought helps us today to illuminate the relationship between science, philosophy, and religion around the subjects of sustainability and ecology. Influential voices in history have essentially argued in favor of the hierarchical exploitation of nature and non-sustainable ecological practices. However, other important voices have identified sustainability as a crucial dimension of our ideal religious and metaphysical stance. The issue of species extinction in particular highlights how thinkers, both ancient and modern, explore the relationship between sustainability, ecology, religion, and philosophy. A goal of ecological sustainability is not only metaphysically possible within the history of western scientific and religious thinking, but also justified by thinkers ranging from Pliny the Elder to Alexander von Humboldt and beyond.