A Brief History of Scientific Naturalism
Ignacio Prado, Tufts University
I had experienced the Ionian Enchantment. It means a belief in the unity of the sciences—a conviction, far deeper than a mere working proposition, that the world is orderly and can be explained by a small number of laws.
- E.O. Wilson, Consilience: The Unity of Knowledge, pp. 4-5.
This is good news, because progress in the natural sciences over the last 500 years has provided us with the methods to acquire reliable knowledge about the world of which we are a part. Rather than a mere act of faith taken on authority, the naturalist’s intellectual convictions about the forces governing the material universe are inspired by this scientific progress, as well as by the failure of appeals to the supernatural to command rational acceptance across different cultural communities or even to maintain internal coherence and plausibility. And the successes of the naturalistic worldview go beyond mere intellectual achievements. The extension of theoretical knowledge made possible by modern scientific investigation has been endlessly and creatively applied in the development of new technologies and means for social cooperation. These advances have given human beings unprecedented power in predicting, controlling, and protecting nature, all in the service of our flourishing on Earth. The history of naturalism I provide here is consequently a thematic overview of a chain of successes, what we might regard as the fruits of our long love affair with the natural world and the intellectual struggle to see ourselves as fundamentally included in it.
In understanding the naturalist as someone who experiences the Ionian Enchantment, E.O. Wilson follows a common tradition in crediting Thales, a philosopher who lived and worked in the Ancient Greek kingdom of Ionia in the 7th Century BCE, as the grandfather of naturalism. Thales held a famously eccentric view that the cosmos was composed of nothing but endless modifications of a single material substance, water. The title “First Naturalist” is doubly appropriate for Thales because, in addition to his materialist views of the nature of reality, he also reputedly made the first successful prediction of a solar eclipse using recognizably modern methods of knowledge acquisition: detailed astronomical observation and mathematical calculation. Though Thales is a standard choice for inaugurating the history of naturalism, Wilson could have easily credited those anonymous members of early human communities of 250,000 years ago. Deploying their biologically evolved capacities for curiosity, rationality, and communicative language, these early humans developed sophisticated arrangements of social cooperation and a spectrum of tools—spears and spades, flints and flutes—that allowed them to reliably control and harness the forces of nature to enhance the well-being of their communities. The empirical, practical stance driving naturalism can thus be understood as a functional adaptation built into our very minds.
Thales made the crucial step, however, of conceiving the entirety of the natural world as a realm of insensate matter and impersonal forces that operate independently of human or supernatural volition. Other ancient Greeks would follow him in this, expunging the Olympian gods from any causal-explanatory role in their theories of the source of order and meaning in nature. Some, like the famous sophist Protagoras, thought that knowledge could exist without the guidance of divinely inspired prophets or culturally authoritative texts, insisting that it could be grounded in the art of critical reflection and rational argument, what became known as dialectic. Protagoras gave agnosticism - the suspension of belief in the existence of gods for lack of evidence - its founding statement when he said, “Concerning the gods, I have no means of knowing whether they exist or not or of what sort they may be. Many things prevent knowledge, including the obscurity of the subject and the brevity of human life."
Perhaps an even larger step toward naturalism than Protagoras’ agnosticism were the ethical reflections of the legendary Socrates. In Plato’s dialogue the Euthyphro, Socrates articulates a famous logical dilemma that challenges the coherence of any ethics that grounds human beings’ moral duties in the commands or will of a divinity. Socrates notes that (i) either the things of value to human life would be valuable independently of the will of the gods, or they wouldn’t. If human values (ii) were independent of the gods’ will, then gods cannot be the ultimate source of human value, since these values would exist even if the gods did not. However, the other side of dilemma convicts theistic ethics of incoherence as well, for if human values (iii) were not independent on the will of the gods—if values followed directly and essentially from what the gods decree—then two counter-intuitive consequences result: (a) actions like murder might have been good if the gods had so deemed them and still might be good if they are so deemed in the future, and (b) our duty to obey the gods cannot be explained, for claiming that duty to be a human good would be viciously circular—asking us to follow the gods’ will because they willed it. Socrates’ arguments in the Euthyphro have been a perennial rebuttal to any ethics that sees morality and human goodness as essentially dependent on the decrees of supernatural agents.
Though these early Greek philosophies were naturalistic in the sense that they abandoned appeals to the volition of gods in explaining events and justifying ethics, they retained a hint of mysticism in conceiving nature to be endowed with nous—a kind of supersensible, mind-like rational ordering of world that provided form and shape to what would be an otherwise formless chaos of matter. The endowment of the natural world with the properties of a rational mind was abandoned, however, by the pre-Socratic philosopher Democritus, who inspired a group of ancient thinkers called “atomists.” The atomists derived their philosophical principles from a view of world as a thoroughly material, disenchanted realm, lacking in mind or spiritual essence and constituted at all levels by different aggregations of material atoms colliding into each other in an otherwise empty void. This strictly material view of the universe implied that observed regularities in nature weren’t a function of supernatural intention, but rather of the properties of inanimate matter itself. Democritus reportedly claimed that “[he] would rather discover a single causal connection than win the throne of Persia.”
Followers of Democritus in the Ancient world included the Hellenistic philosopher, Epicurus, an ethicist who taught that all action should be ruled by a simple maxim: act so as to maintain the highest levels of pleasure in one’s person and society that are consistent with the avoidance of pain. Like their contemporary and competing school of ancient ethicists, the Stoics, the Epicureans conceived of ethics as founded on thoroughly naturalistic principles: each taught, albeit in different ways, that a good human life followed from the use of reason to live in harmony with, rather than antagonism to, the causal principles governing nature and human action. Epicurus said, for example, that “if you do not on every occasion refer each of your actions to the ultimate end prescribed by nature [i.e., the pursuit of pleasure], but instead of this in the act of choice or avoidance turn to some other end, your actions will not be consistent with your theories, because your theories will be false.” Another atomist thinker was the ancient Roman philosopher Lucretius, who wrote a long, sophisticated, verse-form treatise in naturalistic philosophy, On The Nature Of Things. Lucretius’s poem eloquently expresses in many passages the sublimity of the naturalistic view of the cosmos: an immense, ordered web of causation that humbles human understanding:
Many summaries of the history of naturalism jump from its early Greek progenitors and Lucretius to the figures of the 16th and 17th century European Renaissance. These were men such as the astronomers Copernicus and Galileo, the natural philosophers Robert Boyle and Francis Bacon, thinkers like Descartes, and the early modern materialists Gassendi and Hobbes, who together developed the intellectual foundations of the modern scientific method and the naturalistic worldview. There are, however, a few developments between the early Ancient period and the Renaissance that would be crucial in creating conditions favorable for modern naturalism. For example, what the ancient Greeks were to the development of reliable theoretical knowledge, the late imperial Romans were to applied knowledge. The Romans were also great social engineers and efficient administrators of the public welfare. Roads, aqueducts, and other still-standing marvels of Roman civil engineering stretched across the Empire and shaped the natural environment in a way that could reliably sustain a globally far-flung, interconnected, and literate culture, one receptive to empiricism. The two dominant schools of philosophy in Rome—Epicureanism and Stoicism—each held that all reality was unified under a single system of causally inter-related events, and that a well-ordered society could be achieved by living in harmony with the principles of nature, that is, by using empirical knowledge to predict, control and flourish.
Unlike modern forms of naturalistic ethics, however, the schools of Roman philosophy considered adherence to their tenets as the obligation of cultural elites. The uneducated classes, by contrast, were to be kept in order by proverbial bread and circuses, as well as by a religion that deified the Emperor and justified the social hierarchy as protected by Roman Law. Paradoxically, the rise of Christianity – justifiably seen as antithetical to naturalism – ultimately worked in its favor by enabling (unintentionally, of course) the democratization and secularization of authority. It is of course true that the Christian Church dominated all centers of learning in the Middle Ages, so that scholarship was largely schoolastic, not empirical. The Church actively and effectively discouraged naturalistic, materialist understandings of the world from the time of Emperor Justinian’s closing of the Academy in Athens in 529 CE for its “pagan” philosophy, to the condemnation of Galileo in 1663 for his advocacy of the heliocentric system of planets. Nevertheless, the Christian period led to at least three developments that helped clear the way for modern naturalism: (1) the separation of secular from clerical authority in the public administration of the European feudal kingdoms and then, later, in the nation states of early modern Europe; (2) the formation of an ideal of judicial impartiality, elaborated by Thomas Aquinas, which was grounded on a system of natural law that set out norms applicable to all human beings by virtue of their equality before God and the ends assigned them as his creatures; (3) the development of vernacular languages to teach the Gospel, which, aided eventually by the development of Guttenberg’s printing press, allowed the rapid and reliable distribution of information about the natural world. Each of these developments led to more secular understandings of ethics and the source of intellectual authority than was possible in the ancient world, despite the still reigning background assumption that ultimate good and authority rested in god.
The achievements of the Renaissance humanists who are famous to us today through their literary, artistic, and scientific works—Leonardo Da Vinci, Erasmus, Copernicus, Michelangelo, Galileo, Montaigne, and Shakespeare—were made possible by a reinvestment in the value of two human character traits: worldly curiosity and the rational powers of the educated mind. In the milieu of traditional Christendom, the expression of these values had been considered a sign of sinful, God-defying pride, and their reemergence in the Renaissance cannot be overestimated as factor in the development of the humane arts and sciences: Galileo used the newly invented telescope to serve his desire to explore the heavens, Michelangelo sculpted the monumental David to celebrate the human form, and Montaigne wrote his Essays because he was weary of the superstitious dogmatism—founded on sectarian doctrines regarding the basis of religious authority and otherworldly salvation—that had led to the wars of religion prevalent in his time. Insofar as the works of Renaissance humanists were thought to redound to the greater glory of God, this was a derivative effect, a consequence rather than a cause of their intrinsic value as human creations. Likewise, the values of curiosity and a joy in indulging the powers of human intellect for their own sake eventually drove the scientific revolution that swept European centers of learning in the 17th century, reaching its apogee in 1687 with Isaac Newton’s publication of The Principia. This work became the paradigm of revolutionary science, providing for the first time a set of simple, mathematically expressed natural laws - the principles of universal gravity, mass, and inertia - that described the movement of material bodies both on earth and in the heavens, which had previously been considered two distinct causal realms.
With Newton’s announcement that F = m * a, the Ionian enchantment had produced the first grand equation of mathematical physics, now conceived as a discipline studying the principles that could explain why everything in the visible universe happens in the order and manner that it does. During the century surrounding Newton’s revolution in physics, other empirical discoveries were made and scientific theories developed that would extend and unify the realm of natural causation across almost every field of academic investigation. William Harvey, in On the Movement of the Heart and Blood in Animals, showed that the heart worked much like a mechanical pump in circulating the blood throughout the body. This work effectively ended popular belief in the ancient view that immaterial “animal spirits” flowed through the veins carrying blood to the organs in their wake. Harvey’s treatise began the long road modern science would travel in coming to conceive the processes of organic life as thoroughly mechanical, naturally caused and materially structured – no supernatural or non-material component need be posited. Darwin and modern evolutionary biologists are, in unacknowledged ways, the direct heirs of Harvey’s revolution in anatomy. Similarly, Robert Boyle, an active publicist and apologist for the new mechanical philosophy of nature, showed through various experiments that chemical reactions could be explained entirely as a result of the movement and rearrangement of the material “corpuscles” of the reagents. With the dissemination of Boyle’s work, it was possible to abandon the medieval alchemical notion of a “quintessence” or spiritual essence that enters substances at their creation and provides them with their characteristic form and properties. A modern version of the ancient Democritean view of nature had been given experimental grounding: the whole diversity of forms in nature could be understood as the complex collection and recombination of structurally identical, material atoms.
Although he was a metaphysical dualist who thought mind was categorically distinct from matter, the French philosopher René Descartes also helped to lay the theoretical foundations for a materialist physiology. He held that all the functions of life (with the notable exception of thought and reason in human beings) were to be explained not in terms of the soul, but rather in terms of matter in motion. He drew a sharp distinction between humans and animals. While the former had a mind or soul, the latter could be understood as pure mechanisms. Although Descartes, a dualist, held back from presenting a full-fledged materialist account of man, it was only a matter of time before others would take such a step.
For most of the 17th century, awareness of the new ideas being generated by the scientific revolution was largely confined to the members of special societies for the advancement of scholarship, such as England’s Royal Society and France’s Academie des Sciences. But with the development in the 18th century of what came to be known as the Enlightenment, these new ideas quickly reached the swelling European political class of lay traders, shopkeepers, independent farmers, and early industrialists. A group of French Enlightenment theorists of society called philosophes began to publish pamphlets and journalistic articles that popularized the work of Newton, Harvey, Boyle, and other champions of the new experimental sciences. The philosophes are our earliest model of public intellectuals —learned authors who take it upon themselves to be an intermediary between the general public and scholars working in specialized academic fields. The apogee of this public intellectual project was perhaps the Encyclopedia. Edited by Diderot d’Alembert and other leading figures of the mid-18th Century intellectual scene in France, the Encyclopedia was meant to be a compendium of literally all the knowledge of nature available at the time.
The most significant impact of the philosophes, however, was in the realm of political and social philosophy, where ideas were expressed that would inspire the leaders of the democratic revolutions, first in the British Colonies in the Americas and then in France. Patterning their theory of government on that of the Englishman John Locke in his Second Treatise of Government, the philosophes sought to demystify and naturalize the sources of political authority in society. They abandoned the Medieval view of the world as manifesting a hierarchy of being that originates with God and descends through a chain of spiritual authority, ending in a divinely ordained monarch whose decrees constitute the laws of the state. Instead, they conceived political authority on a secular model: it derives from a hypothetical social contract negotiated among free human beings, establishing a framework of cooperation that provides for mutual advantage and protection. As the political philosopher Jean Jacques Rousseau most famously argued in the Discourse on the Inequality of Man, the sources of injustice and class strife in society were understood by Enlightenment thinkers to result from mystifications and illusions foisted upon on an ignorant public by the clergy, monarchy, and other reactionary forces. The traditional views of the Church, which explained political servitude as the inevitable consequence of human beings’ supposedly sinful and fallen nature, were opposed by Enlightenment figures as an ideology designed to force acceptance of unnatural relations of domination in society. Cultural education and social reform were consequently conceived by the Enlightenment thinkers as a project motivated by the need to allow all human beings’ natural capacities to flourish for the mutual benefit of all.
Three figures of the French Enlightenment, the Marquis de Condorcet, Julien Offray de La Mettrie, and Baron d’Holbach, wrote key works in the intellectual genealogy of contemporary naturalistic philosophy. La Mettrie, a physician, presented a fully materialist and mechanistic view of man in Man, a Machine. In his infamous book, The System of Nature, Baron d’Holbach expressed an uncompromising materialist philosophy that denied the existence of any truths that could not be grounded in the observable operation of natural causes. Following the earlier English naturalists Hobbes and Hume, D’Holbach was among the first to insist that traditional conceptions of the freedom of the will, understood as a kind of non-natural, contra-causal force that could violate laws of nature and render human behavior uncaused, were incoherent and unnecessary for grounding political liberty and moral responsibility. In fact, D’Holbach thought that an understanding of human behavior as naturally caused was a precondition for the intelligibility of ethics:
Providing the positive vision of naturalism that would complement D’Holbach’s polemic against the harms of religious belief and superstition, Condorcet outlined in his Sketch for a Historical Progress of the Human Mind how progress in the sciences of nature would lead to inevitable progress in the scope of human flourishing, including a well-ordered society and fair distribution of resources. Condorcet was also among the first to theorize the moral debt that people owe their descendents, writing presciently that “if [we] have obligations to beings that do not yet exist, these obligations do not consist in giving them life, but in giving them happiness.”
With the gradual spread of the naturalistic worldview throughout the large sectors of the European intellectual class in the 19th Century, a series of humanitarian reform movements were inaugurated that understood disease, war, famine, crime, insanity, slavery, women’s inequality, and poverty as naturally caused and remediable pathologies, not expressions of “original sin” or the reflection of an inalterable social hierarchy. In 19th century Britain, a group of what came to be known as “philosophical radicals” advocated for social reforms proposed by the neo-Epicurean ethical theory known as utilitarianism. This modern ethical philosophy was most systematically defended by Jeremy Bentham in his Principles of Morals and Legislation and John Stuart Mill in Utilitarianism and On Liberty. Aside from being among the first to argue for women’s political equality and animal welfare, Bentham was influential in reinterpreting the foundations of criminal punishment on consequentialist rather than retributivist grounds. Retributivists understand punishment as the infliction of deprivations on law-breakers that are deemed to be justly commensurate with the crimes they have committed, without regard to the possible personal or social benefits of punishment. Consequentialists, by contrast, understand punishment and imprisonment as justified solely by their future-directed tendencies to promote both personal and general welfare, for instance by discouraging crime, rehabilitating criminals, and protecting the public from dangerous individuals. Largely through the dissemination of the consequentialist views espoused by Bentham, Mill, and other reform-minded intellectuals, prisons and insane asylums in Britain and other parts of Western society were gradually transformed from primitive holding-houses for undesirables into increasingly humane rehabilitation centers.
The publication by the English biological naturalist Charles Darwin of the Origin of Species in 1859 provided biology with its fundamental theory of natural selection: that all species, and the whole inter-species complexity of the ecological world, have been derived from a common, single-cell ancestor by a process of random mutation and differential reproductive success. In conjunction with the development of modern genetics, Darwin’s theory, in one stroke, unified the life sciences with the rest of the natural sciences and ended the need to posit supernatural causes in order to explain the order and diversity of nature. Then, as now, Darwin’s theory of evolution was viewed by the popular culture as a threat to certain religiously inspired beliefs, most centrally the belief that the fact and nature of human existence is explained by the purposes of a creator. In the Scopes trial of 1925, Clarence Darrow fought the first of many battles to keep unscientific alternatives to evolution out of biology classrooms in the United States.
Though Darwin’s scientific theories caused political and cultural turmoil, they also helped give birth to a new school of American philosophy, known as naturalism, which emerged as an alternative to traditional philosophy by grounding philosophical thought thoroughly inside nature. Naturalists construed human cognition and evaluative thought as the culmination of natural capacities developed through evolutionary processes of adaptation. Responding to idealism, transcendentalism and dualism, they understood the practice of philosophy to be continuous, more or less, with the scientific project of gaining reliable knowledge of the world, not the establishment of foundational truths independent of empiricism. Writing in the earlier half of the 20th century, John Dewey—a widely read philosopher, theorist of education, cultural critic, and public intellectual—inspired generations of philosophers in the United States with a system he called “pragmatic naturalism.” Other philosophers of the original American naturalist movement, some of whom were allied with the Columbia School of Pragmatism, included George Santayana (“a naturalist before naturalism grew popular” says Saatkamp at the Stanford Encyclopedia of Philosophy), Frederick Woodbridge, Morris R. Cohen and John Randall. Here, at last, naturalism took its place as an explicit worldview (albeit with many variations), based in a broadly empirical, scientific epistemological commitment, but going beyond science by making that very commitment the basis for ontological claims about the world – namely, the denial of the supernatural.
Among later naturalists and pragmatists are included the philosophers Ernest Nagel, Sidney Hook, W.V.O. Quine and Wilfrid Sellars, who, working in the mid-20th century, reimagined philosophy as a discipline continuous with the natural sciences. As suggested above, naturalism differs from traditional philosophy in denying that philosophy has a special method that stands outside of the sciences and thus can ground and interpret their success in producing knowledge. The success of science is nothing other than the fact that it unifies our understanding of nature by supplying predictive, economical explanations that achieve broad consensus, and philosophers contribute mainly by clarifying our concepts and by keeping our assumptions, methods, and logic transparent. Quine and Sellars’ naturalization of philosophical method is now widely, although not universally, accepted in the academic community. Today naturalists are the vast majority in philosophy departments and scientific circles, inside and outside the academy. They are those who, having been struck by the Ionian Enchantment, think that it's best to approach the philosophical problems that perennially attract and puzzle reflective human beings—the nature of consciousness, the self, free will, rationality, and the foundations of ethics and justice—with the tools and results of the natural and human sciences. The sciences are the philosopher’s allies in the quest for reliable knowledge about the world and a practical understanding of how to achieve a good, meaningful, and satisfying human life within it.
Those inclined to take a skeptical stance towards the intellectual commitments of contemporary naturalism often remark on the quasi-religious zeal with which naturalists sometimes deny the usefulness or plausibility of alternative worldviews. It should be clear by now, however, how superficial and misleading this analogy is in characterizing those who hold a naturalistic worldview. Naturalism, though it can be animated by the same sort of passion and gratitude for the fact and nature of human existence that religiosity often assumes, is not a faith in any sense. It is, rather, a system of belief grounded in and justified by the progress in the natural sciences that I have attempted to summarize here. But naturalism goes beyond science in holding that the vision of ourselves as fully natural creatures has important implications for our place in the world and the kind of life that we are capable and deserving of living. Unlike those religious believers who hold fast to the supernatural out of a fear of what its denial might mean for human life, the naturalist is someone who, above all, believes that human dignity need not be bought at the price of illusion, for she knows that the Ionian enchantment resonates with the best and most elevating parts of what the non-naturalist might call her soul.
Note: Thanks to Jim Farmelant for his editorial work in preparing this essay. Please stop by Ignacio Prado's blog, The First Element.
Selected books on or related to naturalism
Wikipedia (1) – metaphysical naturalism
Wikipedia (2) – philosophical naturalism
Stanford Encyclopedia of Philosophy (1) - on naturalism
Stanford Encyclopedia of Philosophy (2) – naturalism and legal philosophy
Stanford Encyclopedia of Philosophy (3) – naturalism and ethics
Secular Web pages on naturalism
Richard Carrier's book and articles on naturalism
Ralph Dumain on naturalism vs. materialism, with many references
Naturalism Research Project of the Center for Inquiry