The ancient Stoics were famous, or infamous, depending on whom one asks, for promulgating doctrines that sounded “paradoxical.” Indeed, Cicero wrote an entire book called Paradoxa Stoicorum, in which he tried to explain six of them. “Paradox” here, however, does not literally mean something that is logically contradictory, or that otherwise appears to violate the laws of logic. Rather, it simply means a notion so odd that it is hard to imagine that serious philosophers — such as the Stoics certainly were — ever actually said that. The Stoic motto “live according to nature” certainly falls into this category. And yet, it is a fundamental aspect of Stoic doctrine, so it is important to understand exactly what the Stoics said, and what they meant by it.
One thing the phrase does not mean is that we should go running naked into the nearest forest, stopping to hug trees from time to time. Another thing it does not mean is an appeal to nature. The latter is a well known informal logical fallacy, and according to G.E. Moore, in his Principia Ethica of 1903, it consists in claiming that “a thing is good because it is ‘natural,’ or bad because it is ‘unnatural.’” (This is related to, but not the same, as David Hume’s is/ought gap, often referred to as the naturalistic fallacy. We will turn to that one in a minute.)
It should be pretty obvious that appealing to nature to determine what is good or bad is not a sound procedure. Vaccines are “unnatural,” meaning that they are human creations (of course humans themselves are part of nature, but you see the distinction), and yet they are good for us, anti-vax pseudoscientific nonsense notwithstanding. By contrast, tsunamis are most definitely natural, and yet they are bad for both human beings and other animals on earth who happened to be so unfortunate as to experience their effects.
The Stoics, as we shall see, were not invoking a logical fallacy when they exhorted us to live according to nature. What they were doing, however, is much closer to rejecting David Hume’s postulation that there is an unbridgeable (or at least, very hard to bridge) gap between is and ought, i.e., between facts about the world and moral values. Here is how Hume himself famously put it, in A Treatise of Human Nature, 1739:
“In every system of morality, which I have hitherto met with, I have always remarked, that the author proceeds for some time in the ordinary way of reasoning, and establishes the being of a God, or makes observations concerning human affairs; when of a sudden I am surprised to find, that instead of the usual copulations of propositions, is, and is not, I meet with no proposition that is not connected with an ought, or an ought not. This change is imperceptible; but is, however, of the last consequence. For as this ought, or ought not, expresses some new relation or affirmation, ’tis necessary that it should be observed and explained; and at the same time that a reason should be given, for what seems altogether inconceivable, how this new relation can be a deduction from others, which are entirely different from it.”
In truth, it is not clear here whether Hume is saying that the is/ought gap cannot be bridged, or simply warning us that if one wishes to bridge it then one ought (ah!) to provide explicit arguments, and not just accomplish the feat by sleight of hand. In a talk that I gave earlier this year at Oxford I argued for the latter, and connected this to two facts about Hume: (i) he developed a theory of human nature that is compatible with a naturalistic understanding of ethics, and hence with a bridge between is and ought; and (ii) he was actually sympathetic to Stoic philosophy, though not a Stoic himself.
Hume proposed a “progressive” theory of human nature as part of a debate he was involved in with some of his most esteemed contemporaries, Bernard Mandeville, Francis Hutcheson, and the Earl of Salisbury, Anthony Cooper.
Briefly, Mandeville argued that human beings are naturally self-interested, while Hutcheson and Cooper thought that we are naturally benevolent. Hume came down somewhere in the middle, suggesting that human nature is really a mix of the two, as we both have instincts that are aimed at self preservation as well as instincts that make us a naturally social and cooperative animal. Our social virtues, Hume added, then develop further because of reflection, cultural forces, and habit:
“’Tis by society alone [that man] is able to supply his defects. … By society all his infirmities are compensated and tho’ in that situation his wants multiply every moment on him, yet his abilities are still more augmented and leave him in every respect more satisfied and happy than ‘tis possible for him in his savage and solitary condition, ever to become.” (A Treatise of Human Nature, 479)
Hume scholar Michael Gill explains: “People initially care about justice [and other socially valuable virtues] because it accords with self-interest, [Hume] tells us here. But over time, they develop mental associations that lead them to approve of justice even when it does not promote their self-interest, and to disapprove of injustice even when it does promote their self-interest.” (Hume’s progressive view of human nature, Hume Studies XXVI.1:87-108, 2000)
As we shall see, this is the Enlightenment version of the Stoic “cradle argument,” and does, in fact, provide the basis for a philosophically sound bridging of the is/ought gap. It is also part of the justification for the Stoic dictum that we should live according to nature.
Let’s turn now to the Stoics. In volume III of De Finibus Bonorum et Malorum (On the Ends of Good and Evil; Cicero imagines Cato the Younger explaining things to him:
“It is the view of those whose system I adopt, that immediately upon birth (for that is the proper point to start from) a living creature feels an attachment for itself, and an impulse to preserve itself and to feel affection for its own constitution and for those things which tend to preserve that constitution … Infants desire things conducive to their health and reject things that are the opposite before they have ever felt pleasure or pain; this would not be the case, unless they felt an affection for their own constitution and were afraid of destruction.” (III.5)
“Man’s first attraction is towards the things in accordance with nature; but as soon as he has understanding, or rather become capable of ‘conception’ … and has discerned the order and so to speak harmony that governs conduct, he thereupon esteems this harmony far more highly than all the things for which he originally felt an affection, and by exercise of intelligence and reason infers the conclusion that herein resides the Chief Good of man, the thing that is praiseworthy and desirable for its own sake [i.e., moral virtue].” (III.21)
It should be clear why this is essentially Hume’s view or, rather, the other way around, since Hume not only lived 18 centuries after Cicero, but we have direct evidence that he was influenced by the Stoics. It should also be clear why this is often referred to as the cradle argument: it is a developmental account of how we gradually move from purely selfish interests to more and more socially oriented ones, as a result of upbringing (chiefly, teachings from our caretakers), as well as our own ability to reflect on what makes sense and what doesn’t, and to behave accordingly.
The other major source on the Stoic idea of living according to nature is Diogenes Laertius, who in book VII of the Lives and Opinions of the Eminent Philosophers wrote:
“An animal’s first impulse, say the Stoics, is to self preservation, because nature from the outset endears it to itself, as Chrysippus affirms in the first book of his work On Ends: his words are, ‘The dearest thing to every animal is its own constitution and its consciousness thereof’; for it was not likely that nature should estrange the living thing from itself or that she should leave the creature she has made without either estrangement from or affection for its own constitution. We are forced then to conclude that nature in constituting the animal made it near and dear to itself; for so it comes to repel all that is injurious and give free access to all that is serviceable or akin to it.’ For [animals], say the Stoics, Nature’s rule is to follow the direction of impulse. But when reason by way of a more perfect leadership has been bestowed on the beings we call rational, for them life according to reason rightly becomes the natural life. For reason supervenes to shape impulse scientifically. This is why Zeno was the first (in his treatise On the Nature of Man) to designate as the end ‘life in agreement with nature’ (or living agreeably to nature), which is the same as a virtuous life, virtue being the goal towards which nature guides us. So too Cleanthes in his treatise On Pleasure, as also Posidonius, and Hecato in his work On Ends. Again, living virtuously is equivalent to living in accordance with experience of the actual course of nature, as Chrysippus says in the first book of his De Finibus; for our individual natures are parts of the nature of the whole universe. And this is why the end may be defined as life in accordance with nature, or, in other words, in accordance with our own human nature as well as that of the universe, a life in which we refrain from every action forbidden by the law common to all things, that is to say, the right reason which pervades all things … Diogenes [of Babylon] then expressly declares the end to be to act with good reason in the selection of what is natural. Archedemus says the end is to live in the performance of all befitting actions.” (VII.85-88)
Several things need to be observed in the long passage above. To begin with, again, this is a developmental account of human social psychology. Second, Diogenes tells us that this notion appeared at the very beginning of Stoic philosophy, with Zeno, Cleanthes, and Chrysippus, respectively the first, second, and third heads of the Stoa. Finally, living according to nature in the sense above leads us to live virtuously, because the virtues (practical wisdom, courage, justice, and temperance) are the means by which we rationally govern our intercourse with fellow human beings. Or as Socrates says in the Euthydemus , virtue is the chief good because it is the only thing that can never be used for ill (unlike wealth, health, education, and all the other preferred indifferents).
As I have explained, the cradle argument has been reconstructed in a philosophically sound way, and one moreover that agrees with modern cognitive science, by Larry Becker in his A New Stoicism:
“We may begin life as greedy little egoists, but it is clear enough that we soon spontaneously develop matching affective responses to what we read as signs of others’ pleasures and pains. Cognitive development is relentlessly recursive — ‘leg over leg’ as Piagetians say — in the sense that whatever conceptual schemas we develop and whatever content we acquire in them themselves become the objects of (and determinants of) our subsequent development. As we develop and begin to use the ability to represent this purposive activity symbolically … and begin to manipulate those symbolic representations logically, a secondary form of agency arises, driven by this representational and logical activity. … The process of deliberation and choice becomes a determinative condition of (some of) our conduct.” (Ch. 6)
My original research background is in evolutionary biology, and it is interesting to me that the above meshes very nicely with what primatologists have discovered about our close evolutionary kins over the past couple of decades or so. Just check out Frans de Waal’s “Primates and Philosophers” for a good sense of a combined scientific and philosophical approach to the evolution of morality. Studies conducted on chimpanzees, macaques, rhesus monkeys, and capuchin monkeys show the presence in social primates of four building blocks of morality: empathy, the ability to learn and follow social rules, reciprocity, and peace making. So the life sciences tell us that the building blocks of morality are found (and presumably selected for) in non-human social primates. In the light of modern science, the phrase “live according to nature” takes an enlarged, empirically substantiated meaning.
It is also interesting to note that the words “ethics” and “morality” themselves have revealing roots: the first one comes from the Greek êthos, a word related to our idea of character; the second one is from the Latin moralis, which has to do with habits and customs. Ethics or morality, in the ancient sense, then, is what we do in order to live well together — just like our primate cousins, except of course that unlike bonobos and capuchin monkeys, we can articulate and reflect on our own behaviors, which leads us to the more sophisticated, rationally based sense of living according to nature that the Stoics were defending.
As for modern cognitive sciences, which I see as an extension of the life sciences to the special case of humans, Jean Piaget found that young children are focused on authority mandates, and that with age children become autonomous, evaluating actions from a set of independent principles of morality. Famously, Lawrence Kohlberg expanded upon Piagetian notions of moral development to arrive at his three-level classification of attitudes toward morality:
Subsequently, Elliot Turiel has argued for a social domain approach to social cognition, delineating how individuals differentiate moral (fairness, equality, justice), societal (conventions, group functioning, traditions), and psychological (personal, individual prerogative) concepts from early in development throughout their lifespan. Over the past 40 years, research findings — including cross-cultural studies — have supported this model. (The Handbook of Moral Development, edited by Melanie Killen and Judith Smetana, summarizes the relevant literature while covering a large range of related topics. Also, I am aware that Piaget’s and Kohlberg’s original articulation of their ideas has been criticized, but the general picture seems to hold as much as anything else in developmental moral psychology.)
The way I see it, evolutionary biology, cognitive science, and philosophy provide us with a fuller picture of ethics. The first one tells us something about why we have a moral instinct in the first place (we are inherently social animals, so natural selection favored the evolution of pro-social behaviors); the second one informs us about how modern human beings, with their large brains and cultural milieu, develop complex views of morality from infancy through adulthood; and the third one helps us further develop the logical consequences of our own thinking about how to relate to others, for instance arriving at the related Stoic principles of oikeiôsis and cosmopolitanism, famously articulated by Hierocles with his ideas of a series of contracting circles of concern:
We can therefore, and without fear of committing any logical fallacy, happily agree with Epictetus:
“What should we do then? Make the best use of what is in our power, and treat the rest in accordance with its nature.” (Discourses I.1.17)