Matter

Plato does not use the word "matter" in its later technical sense, but in the Timaeus he introduces what becomes its ancestor: the receptacle, or chora, a third kind of reality alongside the eternal Forms and the sensible copies that come to be in imitation of them. The receptacle is that in which change occurs, a nurse of generation, a space or medium that receives the impressions of the Forms and provides sensible things their place.

The receptacle must itself be characterless. If it already possessed a shape or quality of its own, it could not faithfully take on the character of whatever enters it. Plato accordingly describes it as "invisible and formless, all-embracing," and compares it to the neutral base a perfumer uses before adding scent, or gold from which countless figures may be cast. It never departs from its own nature, yet it is never any particular thing. Here is the origin of the idea of a substratum: something underlying change that is not itself one of the things that change.

Plato's doctrine of the receptacle may be interpreted in more than one way. Some commentators conceive of it as space, others as matter. In either reading, the receptacle serves to explain how the perfect Forms can have imperfect, shifting images in a world of becoming. It is a medium of participation, neither fully being nor fully non-being. What later Platonists, and Aristotle after them, will call prime matter or pure potentiality finds its earliest formulation in this conception. The relation of the receptacle to the Forms is discussed more fully under the idea of Form.

With the receptacle, Plato raises a problem that recurs throughout the tradition: how to conceive a bare substratum that is not itself a being, yet without which no sensible being could come to be. Aristotle and Plotinus each attempt to answer this question in their own terms.

Aristotle reformulates Plato's receptacle as a precise metaphysical principle. To make sense of change, he argues in Physics I, three factors are required: the form that comes to be, the privation that is overcome, and the underlying substratum that persists through the change. That substratum he calls hyle, matter. When bronze becomes a statue, the bronze is the matter, the shape is the form, and the prior formlessness is the privation. Every natural substance, on this account, is a composite of matter and form.

Change, however, does not stop at bronze and wood. When substances themselves come to be and perish, as when wood burns to ash or an organism dies, even substantial forms are exchanged. Beneath all such transformations Aristotle posits what he calls prime matter: pure potentiality, without form, knowable only "by analogy." Prime matter cannot exist on its own, for to exist is to be actual, and prime matter is pure capacity. It is the ultimate receptive principle of the physical world, the condition for anything's being this rather than that. The relation of matter to form as co-principles of change is treated more fully under the idea of Change.

Matter also explains individuation. The form "human" is one; the many human beings differ because each form is realized in a distinct parcel of matter. Matter is thus the principle by which universals become particulars, by which "this flesh and these bones" differ from that flesh and those bones. Because matter carries potentiality, it is also the source of mutability: whatever is material is capable of change precisely because it is not fully actual.

Aristotle's account leaves a difficult question in plain view: prime matter, knowable only by analogy, neither exists nor can be thought without form, yet it must be posited to explain change. When Descartes later identifies matter with extension, he attempts to close this gap by making matter fully intelligible, but in doing so he may lose precisely what Aristotle's prime matter was meant to explain: why things change rather than merely rearrange.

Lucretius, transmitting the philosophy of Epicurus, defends an uncompromising materialism: the universe consists of nothing but atoms moving through void. The atoms are eternal, indivisible, imperceptibly small, and endowed only with size, shape, weight, and motion. Everything else, including color, taste, sound, life, and thought, arises from their combinations and collisions. There is no demiurge, no receptacle, no hylomorphic form, no providence. Matter, on this view, is sufficient to account for all the phenomena of nature.

The argument proceeds from two premises: nothing comes from nothing, and nothing returns to nothing. If matter could vanish, the world would long ago have dissolved; if it could arise from nothing, things would emerge without seeds and grown men would spring from the sea. The conservation of being demands that underlying all change there be imperishable bodies. These atoms move through empty space, swerve unpredictably, and by their combinations constitute the sensible world. The soul itself, for Lucretius, is a particular arrangement of fine, swift atoms, and accordingly perishes with the body. The atomistic conception of matter and its elements is discussed more fully under the idea of Element.

Lucretius connects his physics to an ethical purpose. By showing that everything, including the gods, is composed of ordinary matter, he aims to free human beings from fear of divine wrath and of death. If matter is all there is, then the gods do not interfere with human affairs, and death is merely dissolution. His materialism thus has a therapeutic intention: knowledge of the nature of things is meant to dissolve the anxieties that darken human life.

Lucretius transmits the most complete ancient statement of atomism. When mechanical philosophy revives in the seventeenth century, it is to this Epicurean legacy of atoms, void, and motion that Gassendi, Hobbes, and Newton in various ways return.

Plotinus combines Plato's doctrine of the receptacle with Aristotle's theory of prime matter and carries the result to what may be its furthest metaphysical consequence. In the Neoplatonic hierarchy, reality emanates from the One through Intellect and Soul down to the sensible world. Matter stands at the greatest remove from the source: it is the point at which the procession from the One exhausts itself and nothing further can be generated. Matter is therefore, for Plotinus, non-being, darkness, and absolute privation.

Yet Plotinus does not deny matter a role. It is the receptive principle that allows the forms to appear in the sensible realm; without it there would be no material world at all. Matter, however, contributes nothing of its own. It is "sterile," receptive only, never fertile. Every positive feature that sensible things possess comes from form; matter is the shadow in which those forms are mirrored. Plotinus calls it "the receptacle and nurse of all generation," but he prefers this description to "mother," since matter receives without giving birth. This receptive function of matter is discussed in a different connection under the idea of Form.

Because matter is privation, it is also, for Plotinus, the principle of evil, though not as an active power. Evil, on his account, is the deficiency of being into which soul can fall when it turns away from the One. The descent of soul into matter is a descent toward non-being, and the philosophical life consists in an ascent back toward the higher realities. Plotinus thus assigns to matter a place in the moral order as well as in the cosmological hierarchy.

Plotinus thus establishes the later Platonic conception of matter as the dim boundary of being, necessary yet almost nothing. Augustine draws on this view directly in his Christian metaphysics, and the medieval tradition inherits the question of how matter can be both a creature of God and a principle so close to non-being.

Aquinas takes Aristotle's hylomorphism and locates it within a Christian theology of creation. Physical substances are composites of matter and form; prime matter, or materia prima, is pure potentiality, without actuality or form of its own. Unlike the Neoplatonists, however, Aquinas insists that matter is not non-being or evil. It is part of God's good creation. God does not create formless matter first and then add form; rather, matter and form are concreated together, simultaneously, because matter cannot exist without form even for an instant. The theological implications of creation from nothing are discussed further under the idea of God.

Aquinas refines the Aristotelian analysis in an important respect. Matter, he holds, is twofold: common matter enters into definitions (man is composed of flesh and bones), while signate or individual matter (this flesh, these bones) individuates. Two angels cannot differ in number while agreeing in species, because angels are immaterial and have nothing by which to be numerically distinct. Physical individuals of one species, however, differ by their matter. Matter is thus the principle of individuation, the reason there can be many humans, many horses, many stones of the same kind.

These distinctions bear on epistemology as well. Because the human soul is the form of the body, the human person is a hylomorphic unity. Knowledge begins with sensation of material things and ascends by abstraction: the intellect abstracts from signate matter to common sensible matter (the level of physics), then to common intelligible matter (the level of mathematics), then to being without matter (the level of metaphysics). Aquinas thus differentiates the three speculative sciences in terms of three grades of abstraction from matter.

Aquinas gives the Aristotelian doctrine of matter its most systematic Christian formulation. When Descartes and other early modern philosophers break with scholasticism, it is this framework of prime matter, substantial form, and hylomorphic individuation that they undertake to replace.

Descartes repudiates Aristotelian prime matter and substantial forms together. Matter, he declares, is simply res extensa, extended substance, and its entire essence is three-dimensional extension. Everything traditionally ascribed to bodies, whether qualities, powers, final causes, or substantial forms, is either reducible to modes of extension (size, shape, motion, position) or does not belong to matter at all.

This identification has several notable consequences. If extension is the essence of matter, then there can be no such thing as empty space: where there is extension, there is matter, and the universe is a plenum. Atoms, understood as absolutely indivisible particles, are impossible, since whatever is extended is in principle divisible. Matter is homogeneous throughout the cosmos; the heavens and the earth are made of the same stuff and governed by the same laws of motion. The Aristotelian distinction between terrestrial and celestial matter accordingly falls away. The consequences for the science of mechanics are discussed under the idea of Mechanics.

By making matter nothing but extension, Descartes provides the foundation for a mathematical physics: material nature can be fully described by geometry and the laws of motion that God imparted to matter at creation. At the same time, he must insulate mind from this mechanical universe. Mind is res cogitans, thinking substance, and shares nothing with matter. How two such disjoint substances can interact in the human being becomes one of the central difficulties of the Cartesian system, a problem considered further under the idea of Mind.

With res extensa, Descartes establishes the conception of matter that dominates early modern physics. Matter becomes a single, homogeneous, geometrical substance, amenable to mathematical treatment. Whether this conception can account for all the phenomena of nature, or whether it leaves out something essential, is a question that Spinoza, Locke, and Kant each address in turn.

Hobbes carries the mechanical conception of matter to what may be its most uncompromising conclusion: everything that exists is body in motion. There are no incorporeal substances. Spirits, souls, angels, and even God, if God exists in the universe, must be corporeal. To speak of an "incorporeal substance" is, for Hobbes, to utter words without a referent. Philosophy, on his account, is the science of bodies and their causes.

Sensation, imagination, memory, and reasoning are all, in Hobbes's view, motions of material parts. The objects of sense press on our organs; this pressure is transmitted through nerves to the brain and heart; the resulting internal motions are what we call ideas and passions. Even the state, the "Leviathan," is conceived as an artificial body whose sovereignty arises from the motions of the natural bodies that compose it. Hobbes's political philosophy and his materialism thus form a single system in which man, the commonwealth, and the natural world are all explained mechanically. The bearing of this view on the theory of the state is discussed under the idea of State.

Hobbes removes from matter every scholastic attribution: there are no substantial forms, no final causes, no immaterial minds. If everything is body, then the only laws operative in nature are the laws of motion. The controversy his materialism provoked, including accusations of atheism and of undermining religion and morality, indicates how deeply the tradition had invested in the distinction between the material and the immaterial.

Hobbes's position raises a question that subsequent thinkers must address: if everything, including thought, is matter in motion, then the words that constitute political authority are also physical events, and it becomes difficult to explain the ground of obligation. Locke attempts to meet this difficulty by grounding moral authority in natural law, but the question Hobbes raises about the sufficiency of a purely material account of human life persists throughout the tradition.

Locke accepts the corpuscular philosophy inherited from Boyle and Descartes: bodies are composed of insensibly small particles of matter, and the properties we perceive arise from their bulk, figure, motion, and texture. He sharpens this picture with his distinction between primary and secondary qualities. Primary qualities, such as solidity, extension, figure, motion, and number, really belong to bodies whether perceived or not. Secondary qualities, such as colors, sounds, tastes, smells, and temperatures, are nothing in the bodies themselves but powers, rooted in primary qualities, to produce ideas in us. This distinction between primary and secondary qualities, found also in Lucretius and Descartes, is considered more fully under the ideas of Quality and Sense.

The distinction preserves the mechanistic image of a material world composed of particles in motion and at the same time explains why our sensory experience is so unlike that world. A rose is not literally red; it has a texture of particles that, acting on our eyes, produces the idea of red. Warmth in the fire is one thing; the sensation of pain in the hand is another, though both are caused by the motion of particles. The world as science describes it and the world as we perceive it diverge, yet matter, with its primary qualities, grounds both.

Locke is cautious, however, about the nature of matter itself. When we ask what it is that has these qualities, what the substratum of a body is beyond its observable properties, we find we have no clear idea. Substance in general, Locke confesses, is "something, we know not what," a mere supposition of an unknown support. Matter as extended substance is less transparent than Descartes believed; what we grasp are qualities and ideas, not the inner nature of the thing itself.

Locke's two positions, the distinction between primary and secondary qualities on the one hand and the confession that substance is unknown on the other, set the terms for what follows. Berkeley presses the first to abolish matter entirely; Kant presses the second to ask what, if anything, we can know of things in themselves.

Berkeley takes Locke's empiricism and presses it to a conclusion Locke did not intend: the abolition of matter. If all we ever perceive are ideas, whether colors, sounds, shapes, or tactile sensations, then the supposition of an unperceiving material substance underlying those ideas is both unnecessary and unintelligible. We have no idea of such a substance, and we cannot even conceive it coherently, since to conceive is already to have something before a mind. Esse est percipi: to be is to be perceived.

Berkeley turns Locke's distinction between primary and secondary qualities against itself. If secondary qualities like color and warmth exist only as ideas in minds, the same arguments show that primary qualities such as extension, figure, and motion are equally mind-dependent. One cannot perceive extension without some color or tactile quality; one cannot imagine figure apart from perceived qualities. Primary and secondary qualities stand or fall together, and for Berkeley they all fall on the side of mind. What remains of matter is, in his view, nothing. Material substance is a philosopher's fiction.

Berkeley regards materialism as the root of skepticism and atheism: once a mind-independent material world is posited, the gap between appearance and reality that skeptics exploit is opened, and God's constant agency in nature is made to seem superfluous. By dissolving matter, Berkeley means to secure both common sense, since bodies really are as we perceive them, and religion, since the orderly succession of ideas is sustained directly by the divine mind. Whether his arguments have the same force against all theories of matter, or only against the materialism of Locke and Descartes, is a question raised by those who conceive matter differently, as Aristotle and Aquinas do.

Berkeley's denial of matter is perhaps the most thoroughgoing in the tradition. His arguments require every subsequent philosopher, whether Hume, Kant, or others, to consider whether the concept of matter is a genuine metaphysical category or an unnecessary hypothesis.

Kant addresses both the materialist and the immaterialist by relocating the question of matter altogether. Space and time, he argues, are not properties of things in themselves but the a priori forms of human sensibility. Whatever appears to us appears in space and time because that is how our minds receive what is given. Matter, accordingly, is neither a thing in itself beneath the appearances nor a mere bundle of ideas. Matter is, in Kant's definition, the movable in space: the content of outer intuition, organized by the categories of the understanding into a law-governed nature.

This conception addresses the dispute between Descartes and Berkeley. Against Berkeley, Kant insists that the existence of matter, of bodies in space, is as certain as the existence of the self, because outer intuition is a necessary condition of inner experience. Against Descartes and the dogmatic materialists, he denies that we can know matter as it is in itself. What physics investigates, what the conservation laws describe, what mechanics explains, is matter as appearance: empirically real, yet transcendentally ideal. The relation between appearance and the thing in itself is discussed further under the idea of Being.

In the Metaphysical Foundations of Natural Science, Kant undertakes to show that the basic concept of matter as the movable in space, together with forces of attraction and repulsion and the a priori principles of the understanding, yields the fundamental laws of mechanics. On this view, matter is the lawful correlate of a knowing subject. The earlier debates about whether matter is pure extension, atoms, or potency are thereby reframed: they concern the conditions under which we constitute nature as an object of possible experience.

Kant thus closes one phase of the debate about matter and opens another. Matter is real, lawful, and knowable, but only as appearance. What matter may be in itself remains beyond the reach of theoretical reason. The idealisms and materialisms that follow Kant, including those of Hegel and Marx, contest precisely this limit.

Marx inverts Hegel's idealism and advances a different kind of materialism. For Hegel, Spirit unfolds through history and matter is Spirit's externalization. Marx reverses this: it is material conditions, the modes of production, the organization of labor, and the relations that arise from human beings producing their means of subsistence, that generate consciousness, ideology, religion, and the state. Matter, on this account, is no longer the inert res extensa of Descartes or the appearance of Kant; it is active, historical, and social. The material is what human beings do with nature to reproduce their lives.

This reframes what "materialism" means. Earlier materialisms, whether those of Lucretius, Hobbes, or the eighteenth-century French thinkers, treated matter as atoms in motion and explained human beings as complicated machines. Marx criticizes this as contemplative materialism: it neglects the fact that human beings transform matter through labor, and that labor itself has a history. His dialectical and historical materialism holds that nature and humanity are mediated by production. The senses themselves, he writes in the Manuscripts, are products of human history. The relation between labor and human nature is discussed further under the idea of Labor.

If consciousness is shaped by material conditions, Marx argues, then emancipation cannot come through ideas alone but must come through changing those conditions. Critique of religion becomes critique of politics; critique of politics becomes critique of political economy. Matter, understood as social and historical rather than merely physical, becomes the ground on which questions of human freedom and necessity must be addressed.

With Marx, the concept of matter undergoes its most thorough transformation. What began as Plato's receptacle and Aristotle's prime matter becomes, in his hands, the material conditions of human existence, and the questions traditionally asked about being are recast as questions about the social organization of production.