What Is Naturalism?

Direct Answer

Naturalism is the philosophical view that everything that exists belongs to the natural world — the world described and investigated by the sciences — and that nothing supernatural stands behind, above, or beyond it. There are no Platonic Forms outside space and time, no Cartesian mental substance separate from the physical body, no divine interventions that suspend natural law. Reality, on this view, is a single, continuous order, and the human mind is a part of that order rather than an observer standing outside it.

This does not mean that naturalism is simply materialism — the claim that only physical stuff exists. Many naturalists are materialists, but naturalism as a philosophical position is broader: it holds that whatever exists is natural, and that what counts as "natural" is determined by the ongoing methods of scientific inquiry rather than by a prior commitment to a particular ontology. Consciousness, meaning, value, and normativity may not be reducible to atoms in motion, but naturalists argue that they must be understood as features of the natural world — as phenomena that emerge from and depend on natural processes — rather than as evidence of a non-natural realm.

Naturalism is therefore as much a methodological commitment as a metaphysical one. It says: when we want to understand something — whether it is the motion of planets, the origin of species, the nature of consciousness, or the foundations of morality — we should look to the methods of empirical inquiry rather than to revelation, intuition, or a priori reasoning alone. Philosophy, on this view, is continuous with science: it clarifies concepts, examines assumptions, and probes the implications of scientific findings, but it does not claim access to a separate domain of truth that science cannot reach.

Historical Context

The roots of naturalism extend to ancient Greek philosophy. Aristotle, though not a naturalist in the modern sense, laid important groundwork by insisting that knowledge of nature begins with empirical observation and that the soul is the form of a natural body rather than an independent substance. His biological works — the detailed studies of animals, reproduction, and natural processes — represent the most sustained empirical investigation of the natural world in antiquity, and his method of starting from what is observable and moving toward explanations reflects a naturalist temperament.

The modern naturalist tradition begins in earnest with David Hume in the eighteenth century. Hume's philosophy is naturalist in two related senses. First, he applies the empirical method to every domain of inquiry, including the mind itself: the Treatise of Human Nature attempts to introduce the experimental method of reasoning into moral subjects. Second, Hume offers naturalistic explanations for phenomena that had been attributed to supernatural or rational foundations. Causation is not a necessary connection perceived by reason but a habit of the mind produced by repeated experience. Moral distinctions are not derived from divine command or rational insight but from sentiments of approval and disapproval that are part of human nature. The self is not a simple substance but a bundle of perceptions.

In the nineteenth and twentieth centuries, naturalism became one of the dominant philosophical orientations. John Dewey developed a pragmatic naturalism that placed experience, inquiry, and intelligence at the center of philosophy, arguing that mind, meaning, and value are natural phenomena that emerge in the course of organisms interacting with their environments. W.V.O. Quine argued for a thoroughgoing naturalized epistemology, in which the theory of knowledge is itself a chapter of empirical psychology. Contemporary naturalists such as Daniel Dennett, Patricia Churchland, and David Papineau have extended naturalism into the philosophy of mind, ethics, and the theory of meaning.

Philosophical Perspectives

Metaphysical Naturalism

Metaphysical naturalism is the ontological thesis that reality is exhausted by the natural world. There are no supernatural entities — no God, no souls, no Platonic Forms, no noumenal realm behind appearances. Everything that exists is part of the spatiotemporal causal order investigated by science. This is a strong claim, and it immediately raises the question of what counts as "natural." Naturalists have generally answered that the natural is whatever is accessible to scientific inquiry, either actually or in principle. If science were to discover phenomena that required fundamentally new categories — as quantum mechanics required categories beyond classical physics — those phenomena would still be natural, because they would be integrated into the scientific understanding of the world.

The central argument for metaphysical naturalism is the success of science. Over four centuries, scientific inquiry has progressively explained phenomena that were once attributed to supernatural causes — disease, weather, consciousness, the origin of species, the structure of the cosmos. Naturalists argue that this track record provides strong inductive evidence that all phenomena, including those not yet explained, will ultimately yield to naturalistic explanation. The "God of the gaps" strategy — invoking the supernatural to explain what science has not yet explained — has been progressively undermined as the gaps have closed.

Methodological Naturalism

Methodological naturalism is the epistemological thesis that scientific inquiry should proceed as if naturalism were true, regardless of whether it actually is. This is a weaker claim: it does not assert that the supernatural does not exist, only that science, as a method, is restricted to natural causes and explanations. A methodological naturalist can be religious in private life while insisting that scientific explanations must invoke only natural processes.

This distinction is important in debates about science education and the boundaries of scientific authority. Methodological naturalism is widely accepted as a rule of scientific practice — science seeks natural explanations because that is what its methods are designed to find — but it leaves open the philosophical question of whether the restriction is merely practical or reflects the actual structure of reality. Metaphysical naturalists argue that the success of methodological naturalism is itself evidence for metaphysical naturalism: if the world were not natural, why would restricting inquiry to natural explanations work so well?

Ethical Naturalism

Ethical naturalism holds that moral properties and facts are part of the natural world and can be investigated by empirical methods. Moral truths, on this view, are truths about human flourishing, social cooperation, and the conditions under which beings like us thrive — and these are matters that can be studied scientifically. This position contrasts with ethical non-naturalism (which holds that moral properties are sui generis and not reducible to natural properties) and with divine command theory (which grounds morality in supernatural authority).

Aristotle's ethics is a paradigm of ethical naturalism: he begins from observations about human nature and argues that virtue is the condition under which human beings flourish, just as health is the condition under which the body functions well. Dewey extended this approach by arguing that moral inquiry is a form of practical problem-solving that uses intelligence to determine what conduct will promote the growth and well-being of individuals and communities.

Modern Reflection

Naturalism faces several significant philosophical challenges. The problem of consciousness — how subjective experience, qualia, and first-person awareness can arise from physical processes in the brain — is perhaps the most pressing. Thomas Nagel has argued that consciousness may require a fundamentally new framework that is neither physicalist nor dualist, and that the current naturalistic picture leaves something essential out. The problem of normativity — how facts about what ought to be the case can be grounded in facts about what is the case — challenges ethical naturalism, which must explain how moral obligations can be natural facts without collapsing into mere descriptions of preferences.

Despite these challenges, naturalism remains the default orientation of much contemporary philosophy. Its influence extends beyond academia into the broader culture: the assumption that the natural sciences provide the most reliable account of reality shapes public policy, education, medicine, and technology. The philosophical task is not merely to defend or attack naturalism but to clarify its commitments, examine its limits, and determine how much of human experience — consciousness, value, meaning, freedom — can be understood within its framework and how much resists naturalistic assimilation.

Related Thinkers

• Aristotle — laid the groundwork for naturalism through his empirical method and his insistence that the soul is the form of a natural body, making the mind a feature of the natural world rather than a separate substance.
• David Hume — brought the experimental method to moral subjects, offering naturalistic explanations for causation, morality, and the self that replaced supernatural and rationalist foundations with habits, sentiments, and perceptions.
• John Dewey — developed pragmatic naturalism, arguing that mind, meaning, and value are natural phenomena emerging from the interaction of organisms with their environments, and that philosophy is continuous with scientific inquiry.

Related Quotes

• "Knowledge itself is power." — Francis Bacon (on the naturalist commitment to empirical inquiry)
• "Reason is, and ought only to be the slave of the passions." — David Hume (on the naturalistic explanation of moral motivation)

Related Topics

• Knowledge and Truth — naturalism's epistemological dimension, which treats scientific inquiry as the most reliable route to knowledge.
• Understanding Reality — the collection that gathers ZHAIBIAN's resources on the nature of reality, of which naturalism is one influential philosophical account.

Further Learning

To deepen your understanding of naturalism, explore these connected resources in the ZHAIBIAN archive:

• Reality — the wisdom entry on the nature of what exists, providing the metaphysical context in which naturalism operates.
• Truth — the wisdom entry on truth, exploring the epistemological questions that naturalism addresses through its commitment to scientific method.
• Metaphysics — the philosophy entry on the study of what fundamentally exists, where naturalism makes its strongest ontological claims.
• Epistemology — the philosophy entry on the theory of knowledge, where naturalism argues for the primacy of empirical methods.
• Philosophy of Science — the philosophy entry that examines the methods, assumptions, and limits of the scientific enterprise that naturalism takes as its model.