MATERIALISM

Materialism is the name given to a family of doctrines concerning the nature of the world that give to matter a primary position and accord to mind (or spirit) a secondary, dependent reality or even none at all. Extreme materialism asserts that the real world is spatiotemporal and consists of material things and nothing else, with two important qualifications: first, space and time, or space-time, must also be included if these are realities rather than mere systems of relations, for they are not material things in any straightforward sense. Second, materialism is fundamentally a doctrine concerning the character of the concrete natural world we inhabit, and it is probably best to set to one side controversies over abstract entities such as numbers, or geometric figures, or the relations of entailment and contradiction studied in logic. A strictly extreme materialism would undertake to show that, to the extent that any of these were genuine realities, they are all material in nature, but the issues raised by abstract entities will not be pursued here. It is with extreme materialist views in the concrete realm that this entry is concerned, and in what follows, "materialist" is to be understood in that sense.

Philosophers and scientists have had various views regarding the constitution and behavior of material objects and over whether every material thing is a body, or whether forces, or waves, or fields of force are also realities in their own right. Thus, the cardinal tenet of materialism, "Everything that is, is material," covers a range of different claims.

To accommodate these differences, a material thing can be defined as a being possessing many physical properties and no other properties, or as being made up of parts all of whose properties are physical. The physical properties are position in space and time, size, shape, duration, mass, velocity, solidity, inertia, electric charge, spin, rigidity, temperature, hardness, magnetic field intensity, and the like. The phrase "and the like" is important, for it indicates that any list of physical properties is open-ended. A material thing is one composed of properties that are the object of the science of physics. And physics is a developing science, in which new properties are still being discovered. The question "What counts as a physical property?" thus has no determinate answer. In consequence, there are also no fully determinate answers for the questions "What is a material thing?" and "What does materialism claim?"

This is less serious for materialism than may at first appear, for there is a broad consensus on which properties—among those already known—are the physical ones. And new properties that emerge from research in the physical sciences are, generally speaking, readily identified as belonging among the physical ones rather than representing an anomalous, nonphysical development. It is known well enough what is involved in claiming that something is a material reality, and therefore it is understood well enough what is involved in the various versions of extreme materialism, all of which assert that everything there is, is material.

The psychological characteristics people ascribe to themselves and to one another—consciousness, purposiveness, aspiration, desire, and the ability to perceive, for example—are not considered to be physical properties. So materialism differs from panpsychism, the doctrine that everything material is also at least partly mental or spiritual. Materialism denies the world's basic entities possess these psychological properties. Materialists add that there is no second class of nonmaterial beings in possession of such psychological properties and no others; there are no incorporeal souls or spirits, no spiritual principalities or powers, no angels or devils, no demiurges and no gods (if these are conceived as immaterial entities). Hence, nothing that happens can be attributed to the action of such beings.

The second major tenet of materialism is, accordingly, "Everything that can be explained can be explained on the basis of laws involving only the relevant physical conditions." The differences among materialists over the types of effect material things can have on one another make this second tenet another slogan covering a variety of particular doctrines. Further, although materialists have traditionally been determinists, holding that there is a physical cause for everything that happens, this is not strictly required by materialism itself. Recently, the appeal of determinism has been weakened by the development and success of quantum theory, and many contemporary materialists are not committed to determinism. It should also be mentioned that metaphysical materialism in no way involves an overzealous disposition to pursue money and tangible goods, despite the popular use of "materialistic" to describe this interest.

Nature and Appeal of Materialism

The enduring appeal of materialism arises from its alliance with those sciences that have contributed most to an understanding of the world humans inhabit. Investigations in the physical sciences have a materialist methodology; that is, they attempt to explain a class of phenomena by appeal to physical conditions alone. The claim of materialists is that there is no subject matter that cannot be adequately treated with a materialist methodology. This claim cannot be established by any scientific investigation; it can be established, if at all, only by critical reflection on the whole range of human thought and experience.

Early philosophers proceeded dogmatically, aiming to prove the material nature of the world by mere reflection on what must be. Contemporary materialists are much more modest, offering the claim as a speculative but reasonable generalization from the progress of the physical sciences.

Materialism has been, traditionally, a minority view, indeed a rather daring and scandalous one, but it has made considerable progress over the past century, particularly among educated European peoples. There seem to be three main reasons for this. First, the rise of what might be called "cosmic naturalism"; there has been a decline in those aspects of religious conviction that involve appeal to providential or satanic interventions in the course of events, so that pestilence or climate change, for example, are not attributed to nonmaterial, supernatural forces. Second, the rise of "medical materialism"; the discovery of the biochemical mechanisms involved in neural functioning, and their links to psychological processes, so that it is now taken for granted that thinking, feeling, and the will are subserved by the nervous system, and can be altered by making physical changes by the use of drugs or electrodes. A malfunction of the mind is taken to be a malfunction of the brain. This is a kind of pragmatic materialism—the physical aspects are accorded primacy. Third, the rise of "electronic materialism"; recent years have witnessed an astonishing expansion in the range and sophistication of the mental tasks that digital machines can perform. Not only remembering, recalling, and calculating, but pattern recognition, estimation processes, problem solving, and learning new skills, which hitherto have been the exclusive preserve of living, conscious beings, are now routinely performed by electronic devices that, unless panpsychism is true, are purely physical structures. This has formed the background for an increasingly common assumption that mental activity is a special kind of physical process, which is one critical aspect of materialism.

Materialism remains, nonetheless, a striking and apparently paradoxical doctrine, for it insists that the only differences between human beings and grains of sand prove to be matters of energy flow and structural complexity. People have continued to embrace materialism in the face of the difficulties with which it is beset because it offers a comprehensive, unified account of the nature of reality that is economical, intelligible, and consistent with the most successful of the sciences.

History of Materialism

classical period

Materialism has been a theme in European speculative thought from the earliest periods for which there is any record.

Ionian philosophers in the tradition of Thales (sixth century BCE) attempted to account for the origin and present state of the world by appeal to changes in the state of a fundamental underlying substance (the arche ), which in most cases was held to be of a physical nature. Parmenides of Elea (fifth century BCE) vigorously defended a thoroughgoing monism, maintaining that the world is One, unchanging, eternal, homogeneous, indivisible, indestructible, and without any interior void.

These two threads of thought are combined in the true materialism of Leucippus and his pupil Democritus, who flourished at Abdera in the fifth century BCE. Between them they worked out the first clear conception of matter, the first clear restrictions on the kinds of natural interactions in which material particles could participate, and the first clear program of explanation by appeal to these material interactions alone. The "Great Diakosmos," a lost work written by one or the other (or both), expounded their position. Their basic idea was that the fundamental stuff was of just one kind (matter) and that the fundamental entities were material atoms that were of course by no means unique, but otherwise had all the characteristics of Parmenides' One. These atoms are in constant motion in a void that surrounds them.

Insofar as it can be reconstructed, their doctrine embraced the following theses:

1. Nothing exists but atoms and empty space.
2. Nothing happens by chance (for no reason at all); everything occurs for a reason and of necessity. This necessity is natural and mechanical; it excludes teleological necessitation.
3. Nothing can arise out of nothing; nothing that is can be destroyed. All novelties are merely new combinations or separations of atoms.
4. The atoms are infinite in number and endlessly varied in form, but uniform in composition, being made of the same stuff. They act on one another by pressure or collision only.
5. The great variety of things that we encounter in the world is a consequence of the variety in number, size, shape, and arrangement of the atoms that compose them.
6. The atoms have been in confused random motion from all eternity. This is their natural state and requires no explanation. (Some scholars dispute the attribution of random motion to the atoms and credit the "Great Diakosmos" with advancing the doctrine of an eternal fall through infinite space, which was later presented by Epicurus.)
7. The basic mechanism whereby complex bodies are formed is the collision of two atoms, setting up a vortex. In the vortex motion is communicated from the periphery toward the center. In consequence, heavy atoms move to the center, and there form a body, which is dense relative to the collection of light atoms around the periphery. The vortex continually embraces any new atoms that come near it in their random motion, and it thus begins a world.

This materialist philosophy requires a mechanical account of human sensation. The Leucippus-Democritus account seems to have been ingenious, speculative, and false. Sensation occurs in the human soul, which, like everything else, is composed of atoms. Objects perceptible by the distal senses sight, hearing, or smell, give off effluences, or images, composed of fine, smooth atoms. There are channels in the eyes, ears, and nose along which these effluent atoms pass to collide with the atoms of the soul and produce sensation. Differences of color, in the case of vision, or of pitch, in the case of sound, are due to the varying smoothness or roughness of the incoming image atoms. With the contact senses touch and taste, it is the size and shape of the atoms on the surface of the perceived object that act on soul atoms in the skin or tongue.

Sensory qualities (for example, sweetness, bitterness, temperature, and color) are thus not qualities of the object perceived, which is a collection of atoms, possessed only of physical properties such as size, shape, mass, and hardness. The sensory qualities are, rather, the effects of that collection of atoms on us, that is, on our soul atoms. Here is an early appearance of the distinction between primary and secondary qualities, a distinction every subsequent materialist has also found it necessary to make.

Empedocles (fifth century BCE) founded a medical school in Acragas (Agrigento) in Sicily. His aim was to account in a naturalistic manner for the special features of this world, particularly for the specially organized matter to be found in living creatures. The first appearance of the famous four elements—earth, air, fire, and water—is in his theory. Empedocles seems to have believed that each of these four elements comprised a different type of atom. The creation and dissolution of the macroscopic objects of this world is brought about by the combination and separation of these atoms by two fundamental forces, love and hate, or harmony and discord.

Under the influence of love and hate the world goes through an endless cycle from complete random separation of elements (the triumph of hate), through gradually increasing order, to a complete, calm, spherical, harmonious union (the triumph of love). Hate then begins to exert itself once more. Disintegration sets in, and ultimately the world returns to the state of complete separation of elements. The present state of the world lies between these two extremes. The existence of planetary systems and the origin of animals are thus explained as the influence of love.

Empedocles can be considered a true materialist only if love and hate are either inherent forces in the elemental atoms or themselves material elements with a cementing or corrosive effect on combinations of the other elements; however, he probably thought of them as blind, powerful gods. The rest of his system is similarly ambiguous. On the one hand, he believed in the transmigration of souls and adhered to some kind of Orphic mystery religion; on the other, he gave a mechanical account of sensation, held that the soul was composed of fiery atoms, and said that the blood around the heart is the thought of men. Empedocles' philosophy thus perpetuated the materialist tradition but not in a rigorous or consistent form.

The hostile misinterpretation of his ethics as unworthily hedonistic has made Epicurus (342–270 BCE) the most famous of classical materialists. In his middle age Epicurus came to Athens and founded a school where materialism was taught as the sole foundation of a good life, at once disciplined, calm, serene, and free from superstition.

He adopted the materialist metaphysics of the "Great Diakosmos" but gave a modified account of the origin of worlds. There are an infinite number of atoms falling vertically through an infinite space. In one construction of the Epicurean system the heavier, faster atoms occasionally strike the lighter, slower ones obliquely, giving them a slight lateral velocity. In another construction all atoms fall at uniform velocity, and the original deviations from parallel downward motion are left unexplained.

However caused, the original lateral deviations result in more collisions and deviations and the establishment of vortexes. From these vortexes ordered arrangements of atoms arise. The number of atoms and the time available are unlimited, so every possible arrangement of atoms must occur at some time or another. This world, with its marvelously organized living bodies, is thus just one of the infinite, inevitable arrangements into which the indestructible atoms must fall.

The only Roman author of note in the tradition of materialism is Lucretius (born c. 99 BCE), whose long didactic poem De Rerum Natura gives imaginative sparkle to the metaphysics of Epicurus. Lucretius adopted the second account of the fall of atoms through the void and appealed to some form of voluntary action to explain the original deviations from vertical descent. He thus introduced a nonmechanical source of motion, inconsistent with the remainder of his system.

Like Epicurus, Lucretius was motivated by a wish to free people from the burden of religious fear. He argued passionately and at length against the existence of any spiritual soul and for the mortality of humankind. These beliefs have been explicit features of materialism ever since.

seventeenth century

From the close of the classical period until the Renaissance the church and Aristotle so dominated European speculation that materialist theories virtually lapsed. The revival of materialism is attributable to the work of two seventeenth-century philosophers, Gassendi and Hobbes, who crystallized the naturalistic and skeptical movements of thought that accompanied the rediscovery of antiquity and the rise of natural science. Their most important forerunners were probably Telesio, Campanella, and Cyrano de Bergerac, all of whom attempted to combine materialistic views in physics with a psychology based on sensations.

Pierre Gassendi (1592–1655), who in the last part of his life taught astronomy at the Royal College in Paris, rejected the official Aristotelian philosophy of his time and set about the rehabilitation of Epicureanism. To bring the Epicurean system into closer conformity with Christian doctrine, he claimed that the atoms are not eternal but created. They are finite, not infinite, in number and are organized in our particular world by a providential determination of initial conditions.

Gassendi's materialism extended over physics and psychology, undertaking to account for all inanimate changes and for sensation on a materialist basis. He treated the coming into being of particular things as the accumulation of matter about a seed atom.

But his metaphysics was not, strictly speaking, materialistic, for outside the experienced world Gassendi admitted a creative and providential God and an immaterial and immortal intellect in man distinct from his corporeal soul. There are even some lapses in the physics, too, for Gassendi spoke of gravitation as some kind of movement for self-preservation and allowed that growth from seed atoms may be controlled by formative principles other than the natural motions of atoms.

Thomas Hobbes (1588–1679) was much more consistent and uncompromising. In 1629 he discovered Euclidean geometry and was captivated by its method. During the years that followed he strove to work out a rational philosophy of nature on the Euclidean model.

Hobbes's aim was to discover by cunning analysis of experience the fundamental principles expressing the true nature of everything. The truth of these principles would be manifest to right reason and could thus serve as axioms from which a comprehensive theory of the nature of the world could be deductively derived.

The resulting system is almost pure materialism. Hobbes hoped to use the new non-Aristotelian physics of the seventeenth century as the basis for a final, complete account of reality. From definitions of space and motion he derived the laws of uniform motion. From these, together with a notion of the interaction of bodies, he hoped to proceed to an account of change, thence to an account of sensible change, thence to a theory of the senses and appetites of people, and finally to his notorious civil philosophy.

No part of the universe is not a body, said Hobbes, and no part of the universe contains no body. Hobbes was a plenist, holding all space to be filled by an intangible material ether if nothing else. This doctrine followed directly from his definition of a body as anything existing independently of human thought and having volume. Thus, Hobbes considered God to be a corporeal spirit difficult to distinguish from his eternal, immutable, omnipresent, embodied space, the pervasive ether.

All change in the universe consists in the motion of bodies, so all change reduces to change of position and velocity. Further, nothing can cause a motion but contact with another moving body. The substance of anything is body, and "incorporeal substance" is therefore a contradiction in terms. Hobbes thereby disposed of angels, the soul, and the God of orthodox theology. He departed from strict materialism, however, in his introduction of "conatus" and "impetus" (which are not physical properties) into his account of the initiation of motion and measurement of acceleration. Conatus also enters into Hobbes's account of human sensation and action. Sensations are motions in a person's body, and changes of sensation are changes of that motion. Sensory qualities are really within the perceiver, but by conatus a "phantasm" is projected from the observer onto the observed.

Hobbes was the first to take seriously the problems that language, thought, and logic pose for materialism. He developed a nominalist theory of language and took the subject matter of thought and inference to be phantasms of sense or abstractions from these phantasms. He held, for example, that to remember is to perceive one has perceived. But Hobbes did not make clear just what contact mechanism is at work in mental operations nor whether the phantasms are genuinely corporeal. Thus, in spite of his best efforts, it is doubtful that he developed a fully consistent materialism.

The influence of Gassendi and Hobbes was diminished by the prestige of their brilliant contemporary, Rene Descartes (1596–1650), who accepted a materialist and mechanical account of the inanimate world and the brute creation but insisted that men had immaterial, immortal spirits whose essential nature lay in conscious thought undetermined by causal processes. According to Descartes, there are in the world two quite different sorts of things, extended (material) substances and thinking (spiritual) substances, which are mysteriously united in the case of humankind. He thus crystallized the tradition of dualism (the doctrine that there are just two fundamentally different kinds of substance), which was until recently materialism's chief rival.

eighteenth century

In Epicurus and Lucretius one motive for working out a materialist philosophy was to provide an antidote for the all too prevalent religious terror of their times. With Hobbes, and again in eighteenth-century France, the corresponding motive was opposition to religious oppression. But in addition, rapid growth in physiological knowledge had given rise to the hope that a complete doctrine of man in purely physiological terms was possible and so generated a medical materialism that made the path of the metaphysicians smoother.

Ever since the time of Democritus, materialists had held that the soul consists of fine particles within the body. In the course of the eighteenth century this suggestion was taken up and amplified, and some attempt was made to give it an experiential basis.

An anonymous manuscript, the Ame materielle, written between 1692 and 1704, contains many ingenious explanations of mental function along Democritean lines. Pleasure and pain consist, respectively, of the flow of finer or coarser particles through the channels of the brain. The passions are a matter of the temperature of the heart. Reason consists in the ordering of the soul's fine particles, and the effect of wine in its course through the body is to dislodge some of these fine particles from their proper places. The manuscript is panpsychic in its expression, crediting the atoms with a rudimentary consciousness and will, but it is materialist in substance, for these qualities are not credited with any causal power. The doctrines advanced were purely hypothetical and, as we now know, false. The Ame materielle had successors in Dr. Maubec's Principes physiques de la raison et les passions de l'homme (1709), which again gave a materialist vision of man a panpsychic dress and opposed Descartes's view of the mind as a thinking substance. During the middle years of the century, Denis Diderot's many unsystematic writings took progressively a more materialistic turn. Diderot's Le reve de d'Alembert is a striking hypothetical account of heredity, growth, and the simpler forms of animal behavior in terms of internal motions of living bodies.

The most famous medical materialist is Jean de la Mettrie (1709–1751), a doctor with a philosophical bent whose radical views obliged him to leave a fashionable practice in Paris to live in Holland and Prussia. In L'homme machine (1943 [1748]) he presented a view of the human being as a self-moving machine.

After criticizing all views of the soul as a spiritual entity, La Mettrie proceeded to review all the commonsense evidence for the physical nature of mental activity. He cited the effects of bodily needs, aging, and sleep; he pointed to the analogy of the human body to much "lower" forms, which were not supposed to harbor spiritual minds. Anticipating Pavlov, he spoke of the mechanical basis of speech and of the possibilities of educating deaf-mutes and anthropoid apes. He explained learning to perceive and learning to make moral judgments by appeal to modifications of the brain. Human action is accounted for by the then new doctrine of the stimulus irritability of muscles. La Mettrie embarrassed those who held that the soul is a spiritual unity governing all vital functions by observing the continuing function of organs removed from bodies, the muscular activity of dead or decapitated animals, and the ability of a bisected polyp to grow into two complete ones. He explained conscious sensation and the mental capacities of which we are introspectively aware by means of a magic-lantern analogy, but this was unsatisfactory, for the status of the images involved was not made clear.

The details of La Mettrie's physiology, depending as they do on supposed movements of nervous filaments, are false. However, his program of seeking in neural changes the explanation of mental activity has endured, and his claim that appeals to the actions of a spiritual soul can furnish only pseudo-explanations has gained wide support.

Jean Cabanis (1757–1808), a French doctor, continued this line of thought and in 1802 published Rapports du physique et du moral de l'homme, the most notable innovation of which was to treat the brain as analogous with the digestive system, making sensory impressions its aliments and thoughts its product. The great metaphysical materialist of the period is Paul Heinrich Dietrich d'Holbach (1723–1789), a German nobleman living in Paris. His work the Systeme de la nature was published under a false name "Mirabaud," with a false imprint "London" (Amsterdam) in 1770. This "Bible of all materialism" is speculative philosophy in the grand style; in it the antireligious motive is again uppermost. Holbach maintained that nothing is outside nature. Nature is an uninterrupted and causally determined succession of arrangements of matter in motion. Matter has always existed and always been in motion, and different worlds are formed from different distributions of matter and motion. Matter is of four basic types (earth, air, fire, and water), and changes in their proportions are responsible for all changes other than the spatiotemporal ones that motion without redistribution can accomplish.

Mechanical causes of the impact type, such as collision or compression, are the only intelligible ones, hence the only real ones. Because human beings are in nature and part of nature, all human actions spring from natural causes. The intellectual faculties, thoughts, passions, and will can all be identified with motions hidden within the body. In action outward motions of the limbs are acquired from these internal movements in ways we do not yet understand.

Holbach based the intellectual faculties on feeling and treated feelings as a consequence of certain arrangements of matter. Introspected changes are all changes in our internal material state. Thus, in remembering, we renew in ourselves a previous modification. He treated personal characteristics and temperament in terms of a person's internal structure and interpreted so-called free action not as motiveless action (an absurdity) but as action that, although seeming to flow from a free choice, actually springs from an ultimately unchosen modification of the brain. Holbach's theory of mind is also interesting because in dealing with wit and genius, it suggests the first behavioral analyses of mental concepts. As consistency required, he held the soul to be mortal. The purity of Holbach's materialism is marred only by his admission of relations of sympathy, antipathy, and affinity among material particles, in addition to their unequivocally physical properties, the primary qualities, gravity, and inert force.

The revolution in chemistry that was effected by Joseph Priestley (1777) in England and Antoine-Laurent Lavoisier in France in the 1770s and 1780s was of importance for the later development of materialism, for it established chemistry as a strictly physical science. Since the beginning of the nineteenth century, all properly chemical explanations appeal only to material substances and their natural interactions. Such a chemistry has since been extended in biochemistry to cover all the processes of life, and the case for materialism has thereby been profoundly strengthened. Priestley himself nevertheless vigorously upheld an unorthodox version of Christianity, insisting that the existence of God and the resurrection of the body are not incompatible with a materialist and determinist view of the natural world.

nineteenth century

The philosophers of greatest influence in the nineteenth century—Kant, Fichte, Hegel, Schopenhauer, Lotze, and Mill, for example—were all of an idealist or phenomenalist bent. The dialectical materialism of Friedrich Engels and Karl Marx is not an extreme materialism of the kind discussed here.

Ludwig Buchner, a minor figure, deserves mention as the first to claim explicitly that materialism is a generalization from a posteriori discoveries. In Kraft und Stoff (1855) he claims that we have discovered (not proven a priori ) that there is no force without matter and no matter without force.

There was during this period a continuation of inquiry and speculation on the physiological bases of mental function. Jacob Molescott (1852), Karl Vogt (1846, 1854), and Emil Du Bois-Raymond proceeded with the investigation of physiological processes along biophysical and biochemical lines. The most important developments were scientific findings that undermined the barrier between physical systems and living organisms and thus softened the natural resistances to materialistic theses.

In 1828 the synthesis of urea was achieved, and this refuted the idea that biochemistry was in some way special and distinct from chemistry. In 1847, Hermann Helmholtz established the conservation of energy in organic systems, making still less plausible any claims that living and nonliving systems could not possibly be comprehended in a single theory.

In 1859 Charles Darwin published his Origin of Species, in 1871 his Descent of Man. T. H. Huxley had produced Man's Place in Nature in 1863. These three works at last provided a plausible, empirically grounded case for two of the main planks of materialism, the claim that the organization of living things into forms admirably adapted for survival and reproduction can be explained without appeal to immanent or transcendent purposes, and the claim that humans are a part and product of the natural world. Since then biologists, physiologists, and pathologists have increasingly taken the truth of medical materialism for granted, couching their explanations in physicochemical terms without questioning the propriety or completeness of successful explanations in this form.

twentieth century

The triumphant progress in the twentieth century of a materialistic biology and biochemistry has almost completely eliminated vitalist notions of living forms as governed by forces additional to, and distinct from, the purely physical forces operating on inanimate matter. The situation of earlier ages has been reversed; it now seems implausible to maintain that the vital functions of living organisms are different in kind from chemical (ultimately, physical) processes. In the attempt to demonstrate that something other than matter exists, it is on mind, rather than life, that the opponents of materialism now rely.

Early in the twentieth century, the behaviorist movement arose, in a development linked to the emergence of psychology as a distinct science in its own right, rather than a branch of the philosophy of mind. Many psychologists became disheartened by the difficulties involved in any introspective investigation of inner mental states, and turned to the study of behavior. In its analyses and explanations of human activities, behaviorist psychology relies as far as possible on publicly observable, physical phenomena of stimulus and response. Its aim was to expel the traditionally conceived inner, immaterial mind from psychology, and in this way was a profoundly materialistic development.

In the realm of the mind, a new challenge for immaterialists has also developed. The rise of cybernetics (the abstract theory of machines) and its applications in computing machinery threatens the idea of a special status for mental activity. The gathering and interpretation of information, the employment of stored information, successful and spectacular problem solving, even analogues of fatigue, overload, and confusion, hitherto all found only among complex living organisms, are now displayed by computing hardware, that is, by material structures all of whose operations can be explained in terms of physical properties alone.

Approaching the issue from the opposite direction, experimental study of the nervous systems of animals and of ourselves is showing, in ever-increasing detail, how artificially induced physical changes in the electrochemical state of the nervous system issue in changes in the subject's mental activity. Displays of emotion, performance in perception and recall, and anxiety and tension are being tied down to brain function in this way.

During the twentieth century, there were in fact three distinct movements of a materialistic stamp in the philosophy of mind. In the 1920s and 1930s some logical positivists, led by Rudolph Carnap (1932–1933) and Otto Neurath, espoused an epistemic materialism. They held that the meaning of any statement consists in the directly testable statements deducible from it (the protocol sentences). In order for language and meaning to be public and shared, these protocol sentences must be intersubjectively testable. However, because no statement about one individual's experience or thought or other inner psychological state can be tested by anyone else, only sentences referring to the physical properties of physical entities are intersubjectively testable in the required way. Now, because most statements about minds are incontestably meaningful, they must, despite appearances to the contrary, in fact refer to physical properties and entities, even though translations of them into physical terms cannot be provided. In this way the philosophy of language led to a behaviorist materialism.

The beginnings of translation into behavioral terms was offered for some psychological expressions—for example, "is happy"—by directing attention to the way in which the use of such expressions is taught. A key element in teaching such an expression is to point to people behaving happily. In this emphasis on the conditions under which an expression can be learned, the positivists anticipated the favorite strategy of Ludwig Wittgenstein (1953) and moved away from complete dependence on their general doctrines of meaning and verification.

During the middle years of the twentieth century, the analytic behaviorists, in particular Gilbert Ryle (1949) and his followers, offered to show that descriptions of states of mind are essentially dispositional, so that attributions of intention and intelligence, choice and desire, excitement and fear, and other mental states are all to be understood as attributions of a disposition to behave in a characteristic manner in appropriate circumstances. Dispositions are held by most thinkers to issue from some standing or recurrent underlying state, and with these analytic behaviorists the relevant states underlying human mental life were assumed to be states of the body. Their manifest intention to exorcise any spiritual soul—as Ryle would put it, any "ghost in the machine"—places them in the materialist tradition.

Wittgenstein, although he disdained the title behaviorist, belongs to the same group. He insisted that in any acceptable analysis of a mental concept the description of a person's state of mind must make reference only to publicly detectable features of the organism and its behavior. His many subtle discussions of mental concepts are all attempts to identify the patterns of behavior whose display would constitute being in a given state of mind. To attribute that state of mind to someone is to attribute a disposition to display the relevant pattern of behavior. The alternative analysis that interprets the various states of mind as states and processes in a spiritual soul is, according to Wittgenstein, not merely false, it is unintelligible.

On two key points the analytic behaviorists were not convincing. First, if mental states are dispositions to display particular patterns of behavior, they cannot be causes of the behavior in question. It cannot be that a man's anger made him shout, for the shouting is itself just an aspect of the anger. Nor can a woman's pride have made her stubborn. Yet this causal link between a mental state and the characteristic behavior pattern that springs from it, is at the heart of how we understand one another.

Second, some inner mental episodes, such as afterimages, pains, sudden unsought recollections, dreams, or flashes of insight, resist any plausible dispositional analysis. The mind does seem to be a collection of categorical states, items, or events in addition to a cluster of dispositions. The effort to correct both these weaknesses, first the denial of any categorical component, and later the denial of any causal power to the mind, was a significant factor in materialism's subsequent development.

The third group of twentieth-century materialists embraced a theory of mind known as central-state physicalism, from which contemporary materialism derives. The central-state physicalists held that although it may be that some mental states can be understood dispositionally, there are many mental states, items, or events that must be accorded a straightforwardly categorical status. These categorical mental states turn out to be, as a matter of contingent fact, states of the central nervous system. To introspective awareness they do not seem to be neural states, but the explanation for this is that the nervous system is presented to itself in an opaque or covert fashion.

The mind has many aspects, and mental life underpins almost every distinctively human capacity. Most of our distinctive capacities have been pointed to as showing that a living human being must be something more than a mere assemblage of atoms. To understand ourselves, we cannot do without the concepts of perception, belief, and intelligence; action, decision, and choice; motive, drive, and need; feeling, emotion, and mood; temperament and character. We will also need to treat of consciousness and self-consciousness. The task for materialists is to explain how merely material structures could exhibit all these mental attributes. In attempting this, two basic approaches were at first adopted, the behavioral and the topic neutral.

Behavioral strategy

The central-state physicalists were able to appropriate the earlier work of the behaviorists and accept that the attribution to an organism of some of the mental predicates (for example intelligence, equanimity, or ambition) is in reality the attribution of a disposition to behave in a characteristic way under suitable conditions. The organism displaying the behavior, the form the behavior takes, and the conditions under which it is manifested, are all specifiable in purely physical terms. Moreover, the remarkable subtlety and complexity of human behavior, which until the twentieth century appeared to surpass anything of which a mere machine could be capable, no longer has such immaterialist implications, for now the development of electronic machines suggests that the ability to duplicate human performance is possible. In particular, the self-monitoring features of conscious behavior can be displayed by material systems.

Topic-neutral strategy

Many mental states resist the behavioral strategy: being in pain, seeing a color, or feeling depressed, for example. For these, a different claim was made: To attribute such a state is to assert that there is present within the organism some state or process that typically arises from a particular kind of stimulus and/or typically issues in a characteristic kind of behavior. A burning pain, for example, is a state of a person typically arising from excessive heat on the skin, and characteristically issuing in applications of soothing cream to the affected part. Mental predicates of this kind have been called topic-neutral because they do not specify the nature of the inner state in question. The inner state is not described either as material or as immaterial. To say that someone is in pain, the argument runs, does not of itself imply that the experience belongs to a immaterial mind. It implies only that the person is in some central state or other, arising from the states and processes in the sensory system (input), and issuing in certain behavior patterns (output). When we attempt to identify this central state, we find that the sensory system provides inputs to the organism's central nervous system, which in turn sets in train the muscular movements required for any type of behavior. If inner states admit of the topic-neutral treatment, they, too have no immaterialist implications.

Among early central-state physicalists, some, such as Paul K. Feyerabend (1963) and Hilary Putnam, claimed only that this is the most promising line for investigation to now take. Others, such as U. T. Place (1956), J. J. C. Smart (1959, 1963), and Herbert Feigl (1958), went further and held that any alternative dualist view is already frankly incredible.

Contemporary Materialism

During the later years of the twentieth century, under the influence chiefly of David Armstrong (1968) and David Lewis (1972), the topic-neutral strategy was taken up and developed. The behavioral strategy became less prominent, as more and more mental attributions were interpreted as asserting that the organism was in an appropriate categorical state. And the role of the mental as the causal bridge between stimulus and response was taken up and emphasized. Mental states came to be regarded as theoretical constructs and assimilated to other theoretical entities more familiar from other sciences, as philosophers adopted a third strategy for accounting for mental descriptions in a material world.

causal/theoretical strategy

In a complete departure from the behaviorist viewpoint, which saw mentality as a matter of the outer effects of stimuli, the new position is that the really essential thing about any mental state is its causal role, as the crucial inner intermediary between input and response. The idea is that the activity of conscious living beings calls for explanation, and the most appropriate explanations will attribute to such organisms inner states, produced by environmental and remembered elements, and producing behavior that, in the light of the organism's beliefs, is best suited to fulfilling its purposes.

So the mind becomes an inner, theoretical entity, the that-which-best-accounts-for the phenomena of conscious behavior. The analogy was drawn with the gene in biology, that-which-best-accounts-for the phenomena of heredity, and with lightning, that-which-best-accounts-for flashes, thunder, and some kinds of storm damage.

Then, still following the analogy, the research question becomes that of finding which element in the world turns out to fill the theoretical role in question. Structures crucially involving the DNA molecule, as it turns out, best account for heredity. Electrical discharges, as it turns out, best account for the flashes, rumbles, and damage of electrical storms. This is a matter of the contingent identification of underlying structures and processes as the causal bases for patterns of observed phenomena. So with the mind: It is the central nervous system (brain, optic nerve, spinal chord, and some other components) that, as it turns out, fulfills the mind's causal role as the intermediary and clearinghouse between the inputs, many of which we know as experience, and the outputs that consist in purposive activity.

In this way functionalism, the dominant form of contemporary materialism, developed. It has two components. The first component is a theory of the mind, which asserts that the essential feature of the mind is its causal role, and identifies the different states of mind—beliefs, fears, plans, twinges, and so forth—in terms of their particular places in the whole mental causal scheme. This theory of the nature of mind lends itself to materialism, but is not itself materialist. It is topic-neutral, allowing for any of a number of views of what it is that provides the causal bridge between inputs and responses. The second component in functionalist materialism is the theoretical identification of the mind with the central nervous system. This is a contingent assertion about what minds turn out to be in this world. As such, it is vulnerable to various empirical developments, as all substantial empirical claims should be.

Objections to Materialism

the possibility of scientific refutation

Materialism is a strong version of naturalism. It asserts that everything whatsoever that occurs in this world is the result of the operation of physical forces in accord with physical laws. So a spectacular and unequivocal divine intervention in the course of nature, such as the Apocalypse and the Day of Judgment as described in the book of Revelation, would spell the end of materialism as a credible philosophy.

Less spectacular developments could have the same impact. The firm establishing of parapsychological powers (telepathy, clairvoyance, or psychokinesis) would do so, for by definition any paranormal phenomenon involves knowledge or action by a mind in defiance of physical law. So also would developments in neural science that uncovered variations in effectual states of mind without any appropriate change in states of the central nervous system. Or changes in the central nervous system linked to changes in mental state, such as forming a new resolution, that systematically violate the probabilities for neural change that physical laws set forth and that defy any modification to accepted physical laws.

Materialism, being vulnerable in these ways, remains to that extent speculative. But whereas a watching brief needs to be kept over the progress of scientific investigations, it is fair to say that there is at present no serious threat from these quarters. The credibility of positive paranormal results has, if anything, diminished in the course of the past half century. And we are very far indeed from being able to assert that the activity of the brain is physically anomalous. Quite the contrary; so far, no apparent violations of physical law have been found.

theology

Materialism not only holds that there are no supernatural interventions in the course of nature, but that there are no divine beings of any kind. To defend materialism on these points, one must first show that there is no valid deductive argument for the existence of a necessary being, then sustain the view that this world does not call for a divine creator as the best explanation for its existence and character.

Next, one must deny that religious experience reveals a supernatural realm, as vision provides access to a physical one. Adopting the skeptical empiricists' critique, one can argue that religious experience is not sufficiently uniform, widespread, and unanimous to warrant abandoning the natural modes of explanation that have served so well in all other enquiries, especially as supernatural hypotheses face peculiar difficulties when it comes to putting them to the test. The materialist position is strengthened by the promise of continued success in finding concrete natural explanations of religious experience through developments in sociology, psychology and physiology.

If these positions can be established, claims to the existence of God and the occurrence of miracles are established neither by argument nor in experience and so must be considered as interpretative hypotheses laid upon the experienced world. The materialist must again urge that in framing hypotheses, as in seeking explanations, there is no sufficient reason for deserting the natural for the supernatural. In such circumstances as these considerations of parsimony exclude all supernatural entities from any reasonable ontology.

Materialists must show that, contrary to the claims of Spiritualists and Buddhists, there is no sufficient reason to believe in survival of bodily death or in reincarnation. And indeed there are plausible arguments that both doctrines rest on untenable views of the self. These arguments do not impugn the possibility of bodily resurrection, but that is compatible with materialism.

metaphysics

Materialism has in the past been assailed as incomplete. Even if, in a great advance on its predecessors, modern cosmology does provide explanations for the origin, persistence, and motion of the fundamental particles, it provides none for the initial conditions from which these derive. Nor does materialism make intelligible why each fundamental interaction has had one result and not another. The reply, now widely accepted, is that all chains of explanation must eventually come to a terminus and that to seek to go beyond contingent truths concerning the items and processes in this world is to go hunting a mare's nest.

the mind and human experience

There is no doubt that our own conscious experience provides the greatest intuitive challenge to materialism. C. D. Broad in The Mind and Its Place in Nature (1925) formulates many people's reaction to the suggestion that mental events are physical events, such as molecular movements, taking place in our body:

About a molecular movement it is perfectly reasonable to raise the question "Is it swift or slow, straight or circular and so on?" About the awareness of a red patch it is nonsensical to ask whether it is a swift or slow awareness, a straight or circular awareness, and so on. Conversely, it is reasonable to ask whether it is a clear or a confused awareness, but it is nonsense to ask of a molecular movement whether it is a clear or a confused movement. Thus the attempt to argue that "being a sensation of so and so" and "being a bit of bodily behavior of such and such a kind" are just two names for the same characteristic is evidently hopeless. (p. 623)

Indeed, this attempt is hopeless, but it is not one a materialist must make. We need to distinguish the process of being aware from the item of which we are aware. The two "names" that materialists claim to name the same thing are "subject S having sensation P " and "subject S undergoing bodily changes Q," and it has become clear since Broad wrote that what is or is not nonsensical is not an immediate deliverance of introspection, but an issue in the fashioning of concepts to improve theories of the world. As for P, which is the item of which S is aware—what Broad calls the sensation S has—there would be no absurdity if this could be dealt with by a topic-neutral strategy. We are aware that something is going on in us, which deserves the description "red patch," but according to the topic-neutral strategy, the nature of what is going on is not part of what we are conscious of. The fact of the matter, according to the materialists, is that we have a covert presentation of bodily changes Q to the person S, who is having the sensation. Nevertheless, the two main stumbling blocks for functionalist materialism both concern the character of our inner life.

The qualia problem

The topic-neutral or causal/theoretical strategies may well be satisfactory for those inner states that have no special "feel" about them, such as deciding. We can decide to do something, and be aware that we have decided, but that awareness carries no special feel or twinge or glow with it. We are aware that something is going on in us, something that will have an impact on how we behave by bringing a new causal factor into our life. But that state, and our awareness of that state, reveal nothing about its nature as material or immaterial. Decisions and intentions are thus favorable candidates for a topic-neutral analysis—so, too, is doing mental arithmetic, where the process leads to changes in what one will say or do, but carries no other inner characteristics that one is aware of.

The case is otherwise, however, with sensations and feelings. To see a red patch is to be aware of an inner state that has a redness about it, that sets it apart from the green and blue patches we see. This difference is not obviously a difference in how we discriminate the two items, and react to them, as is brought out by the spectrum-shift arguments, which point out that although your outward color-vision behavior may match mine, you may see reds as I see pale pinks, or blues as I see greens.

To be in love is certainly to be in a state apt to issue in a characteristic pattern of behavior. But it is more than that; there is a complex of feelings involved that do not of themselves involve behavioral differences, but differences in consciousness, by comparison with those not in love.

To be angry, or in pain, or delighted, carry special sensations or feelings with them too. All such sensations or feelings are known as qualia, and the qualia problem is the problem of fitting them in to a materialist world view. It is notorious that when you are seeing something green, and therefore experiencing a sensation of green, there is no green physical surface anywhere inside you. The sharp pangs of pain are similarly elusive—the neural activities have been found that occur when pain is felt, but the painfulness of pain does not seem to be present among them.

Qualia seem to be an important part of being conscious. They seem to make a difference to how we speak and act, yet they stand outside the network of physical causation, neither taking energy in their production, nor having any force to apply to change the world. They challenge the deep materialist commitment to the physical closure of the natural world. If only physical items can have physical effects, then qualia cannot even produce our awareness of them, nor our capacity to describe them, which makes them paradoxical items indeed.

There have been attempts to account for them behavioristically, as dispositions to act and react in particular ways. Perhaps the most promising materialist suggestion is that the intrinsic qualities of sensations are in reality purely schematic and enable us only to distinguish one sensation from another. Inner states notoriously elude direct characterization. Our attempts to describe them often proceed by comparison with other sensations directly or ultimately picked out by reference to their stimulus and/or response. For example, we describe smells as of cinnamon or of rotten eggs (stimulus) and as appetizing or nauseating (response); we speak of pains as jabbing, burning, or like "pins and needles." Feelings of anger, shame, pride, and fear are all described in terms of bodily temperature.

If the sameness or difference of inner states but not their nature is given introspectively, sensations could well be states of the nervous system typically connected with stimulus and/or response, even though we are not aware of this. This strategy for dealing with qualia faces the problems of spectrum-shift arguments, because two sets of sensations, tastes for example, could be shifted relative to one another along a spectrum, yet perform equally well in informing us of the sameness or difference, and typical causes and effects, of our inner states.

The qualia problem was long emphasized by F. C. Jackson (1998) in a series of influential articles. His most recent stance is the "there must be a solution" solution: Somehow, qualia must be reconcilable with materialism, even if we cannot see how.

The insight problem

The second currently most acute problem for materialism concerns the nature of human insight and understanding. When we learn to speak a language, we acquire the ability to conduct a conversation satisfactorily; that is, to make appropriate responses to the speech of others, to initiate conversations using sounds the other recognizes and responds to. But to properly understand, more than linguistic competence is required. This was dramatized by John Searle (1992) in his "Chinese Room" argument: If someone who had no understanding of Chinese but who could recognize Chinese characters were shut away in a room, and provided with pieces of Chinese—questions and so forth—through a mailbox, that person could, using a computerized dictionary for example, choose appropriate Chinese-character responses. This is a linguistic competence that does not include understanding and is clearly deficient by comparison with the capacity of a genuine Chinese speaker. The missing component, understanding or insight, proves just as elusive as do the qualia to materialist studies of the nervous system.

philosophy

Materialism faces several other more general objections, for the most part of a logical kind, that must be faced.

The argument from self-destruction

A popular argument for disposing of materialism is this:

All doctrines concerning the nature of the world are arrived at by inference.

Thus, a fortiori, materialism is so reached.

But if materialism is true, inference is a causally determined process in people's brains, and not a rational process.

Materialism is therefore a doctrine arrived at by nonrational causal processes.

Thus, if it is true, there can be no reason to think it so.

This argument has a long history, being found in Epicurus and developed and defended by J. B. S. Haldane (1932) and Karl Popper (1977). Nevertheless, it is invalid. That the course of a given process of inferring was determined by the structure of a brain does not entail that it was an unreasonable inference. Nor does it entail that there could be no ground for thinking it reasonable. We can see that this is so, by comparing reasoning in people with calculating in adding machines. The result reached is a causal consequence of the structure of the machine; it is nonetheless a correct one, and one we are entitled to rely on. Haldane later retracted his argument (1954).

Asymmetrical knowledge of physical and mental states

Another common argument against materialism points out that, although ordinary people can recognize thoughts and feelings and intentions, they are completely ignorant of processes in the central nervous system, and so the mental occurrences cannot be identified with any such physical events. Friedrich Paulsen, for example, argued to this effect in chapter one of his Introduction to Philosophy (1895 [1892]).

This argument is also, as it stands, invalid. It is like arguing that because the police know some of the characteristics of a man who committed a crime but do not know anything about John Smith, John Smith could not possibly be the man who committed the crime. A similar reply is provided by Place and Smart in articles cited in the bibliography.

The argument would be valid if another premise were added: In introspection the full nature of mental events is disclosed. But there is no good reason for thinking this premise is true.

A variation of this argument claimed that introspective knowledge of our own mental states is incorrigible, whereas no knowledge of anything physical is incorrigible, so mental states cannot be physical. This argument faded from view after Armstrong exposed its weakness: We can and do make mistakes about our own inner mental states.

The general nature of human reason

Keith Gunderson (1964) revived an argument of Descartes's to the effect that men are not machines, even cybernetic machines, and therefore not merely material. In all known machines the matching or surpassing of a human intellectual ability is a specific outcome of a specific structure. Each skill is a skill at some specific task and no other. But in human beings, intellectual skills are generalized and come in clusters; human reason is a tool for all circumstances. Thus, it is not proven that the human skill and that of the machine arise from a like inner structure. On the contrary, the reasonable conclusion is that the machine's skill and the human skill are to be explained in different ways—that is, a person is not any kind of machine.

The reply available to materialists is that this argument is premature. The simulation of human performance by material assemblages is in its infancy. There seems no reason to suppose a machine with generalized skills impossible.

Intentionality

Unlike the situation with anything physical, in the realm of the mind there are relations that can exist even in the absence of one of their terms. These are the intentional relations, which include intending, believing, hoping, fearing, and desiring. The argument from intentionality rests on this peculiarity and may be put this way:

A peculiarity of many mental states is their essential connection with an object. In intending, I must intend something, and in hoping, I must hope for something.

However, whereas when I kick something, the thing I kick must exist, the thing intended or the thing hoped for may or may not have any real existence.

In this way some mental states differ essentially from all physical states.

Thus, materialism cannot be true.

The materialist reply to this argument is that intentional "relations" are strictly speaking not relations but monadic states that are identified by reference to what would fulfill them or constitute their exercise. These are possible states or circumstances that, were they actual, would be material. It is a further question, however, whether the existence of mere, unactualized possibilities is compatible with a strict materialism.

Logical connections between distinct existences

The essential link between a mental state and the behavior to which it gives rise has also been seen to rule out materialism:

Where an intention is carried out, both the intention and the thing intended exist.

They are two different things.

Nevertheless, they are logically connected, because what was carried out makes the intention what it was.

But any two different physical items are only contingently connected.

Hence, mental states cannot be physical items.

Materialists urge in rebuttal that this is a consequence of the peculiarly causal character of mental states and has its counterpart in the uncontroversially physical realm.

Thus if we describe arsenic causally as a lethal poison, there is a logical connection between drinking the lethal poison arsenic and dying, even though the arsenic, the drinking, and the dying, are all distinct existences.

Nonreductive Materialism

Despite the progress made in rebutting the classical objections to materialism, and despite the current popularity, in English-speaking philosophy, of functionalist physicalism as a philosophy of mind, uneasiness remains that materialism accords insufficient recognition to consciousness and its highest expressions—music, literature, love, and fine feeling generally, as well as culture, morality, and religious aspiration. In response to this, there have been some attempts at a softer materialism that tries to accord to the physical a primary but not exclusive place. While everything depends on the physical, it does not reduce to the physico-chemical, but rather supervenes upon it. The most thorough attempt in this direction is J. F. Post's The Faces of Existence (1987). A further step away from extreme materialism is taken in Nicholas Maxwell's The Human World in the Physical Universe (2001), which advocates a dual-aspect position while clinging to the central materialist claim that the universe is a closed system, in which the only causally effective forces are the physical ones.

See also Philosophy of Mind.

Bibliography

general histories of materialism

Lange, Frederick Albert. Geschichte des Materialismus (1865). Translated by E. C. Thomas as The History of Materialism. London: Truebner, 1877–1892. This classic is by far the most important secondary source in the history of materialist theories. All English editions since the London edition of 1925 include an introduction by Bertrand Russell titled "Materialism."

Lewes, George Henry. The Biographical History of Philosophy. London: C. Knight, 1845. A lively and idiosyncratic history, with good comments on materialist philosophers.

Vitzthum, R. Materialism: An Affirmative History and Definition. Amherst, NY: Prometheus, 1995. Accessible work, emphasizing the scientific aspects of the development of materialism.

classical period

Aristotle. Metaphysica. Translated by W. D. Ross as Metaphysics Oxford: Clarendon Press, 1924. Most easily accessible source for ancient world opinion on materialistic Greeks.

Burnet, John. Early Greek Philosophy. 4th ed. London: A & C Black, 1930.

Burnet, John. Greek Philosophy; Thales to Plato. London: Macmillan, 1914. Standard account of ancient philosophy.

Lucretius. De Rerum Natura. Classic presentation, in Latin verse, expanding and occasionally modifying the doctrines of Epicurus. Translated by Rolfe Humphries as The Way Things Are. Bloomington: Indiana University Press, 1969. Another edition, translated by R. E. Latham. Harmondsworth, England: Penguin, 1961.

seventeenth century

Brandt, Frithiof. Den mekaniske Naturopfattelse hos Thomas Hobbes. Translated by Vaughan Maxwell and Annie Fairstoll as Thomas Hobbes' Mechanical Conception of Nature. London: Librairie Hachette, 1928. Detailed and definitive.

Cyrano de Bergerac, Savinien de. Etats et empires de la lune and Etats et empires du soleil. 1657, 1662. Translated by Richard Aldington as Voyages to the Moon and the Sun. New York: Orion Press, 1962. These fictional works epitomize the seventeenth-century movement toward materialism.

Gassendi, Pierre. Animadversiones in Decimum Librum Diogenis Laerti. Lyons, France, 1649.

Gassendi, Pierre. De Vita et Moribus Epicuri Libri Octo. Lyons, France, 1647.

Gassendi, Pierre. Philosophiae Epicuri Syntagma. Lyons, France, 1649.

Gassendi, Pierre. Syntagma Philosophicum. Lyons, France, 1658. These four works appeared together in Opera Omnia. Lyons, France, 1658. Facsimile reprint Stuttgard-Bad-Cannstatt, frommann, 1964. In these four works Gassendi expounds and defends Epicurus (except where his views conflict with Catholic doctrine.)

Hobbes, Thomas. English Works, edited by William Molesworth. London: Bohn, 1839.

Hobbes, Thomas. Latin Works, edited by William Molesworth. London: Bohn, 1839.

Mintz, Samuel I. The Hunting of Leviathan. Cambridge, U.K.: Cambridge University Press, 1962. Narrates contemporary reactions to Hobbes.

Peters, Richard. Hobbes. Harmondsworth: Penguin, 1956. Interesting and comprehensible introduction.

Rochot, Bernard. Les travaux de Gassendi sur Epicure et sur l'atomisme 1619–1658. Paris: Libraire Philosophique, 1944. Most accessible modern treatment of Gassendi.

Spink, John S. French Free-Thought from Gassendi to Voltaire. London: University of London, Athlone Press, 1960.

eighteenth century

Cabanis, Pierre-Jean-Georges. Rapports du physique et du moral de l'homme. Paris, 1802. English translation by M. D. Saidi. Baltimore: Johns Hopkins Press, 1981.

Diderot, Denis. Oeuvres completes. Paris: Garnier Freres, 1875.

Holbach, Paul Heinrich Dietrich d'. Systeme de la nature … par Mirabaud. 1770. Translated by H. D. Robinson as The System of Nature. Edited by Denis Diderot. Boston: J. P. Mendum, 1853. Classic treatise.

La Mettrie, Julien Offray de. L'homme machine. 1748. Translated and edited by Ann Thom as Machine Man. Cambridge, U.K.: Cambridge University Press, 1996. There is also a critical edition with notes by Aram Vartanian. Princeton, 1960.

Maubec. Principes de la raison et les passions de l'homme. Manuscript held in the Bibliotheque nationale in Paris (B.N. n.a.f.r.14709).

Priestley, Joseph. Disquisitions Relating to Matter and Spirit. London: J. Johnson, 1777.

nineteenth century

Buchner, Ludwig. Kraft und Stoff (1855). Translated by J. Frederick Collingwood as Force and Matter. London, Truebner, 1884.

Darwin, Charles. The Descent of Man. New York: Appleton, 1871.

Darwin, Charles. The Origin of Species. London: John Murray, 1859. Classic treatise.

Moleschott, Jakob. Der Kreislauf des Lebens. Mainz, Germany: Von Zabern, 1857.

Passmore, John. A Hundred Years of Philosophy. London: Duckworth, 1957. Readable and authoritative guide.

Vogt, Karl. Kohlerglaube und Wissenschaft. Giessen, Germany: Ricker, 1855.

Vogt, Karl. Physiologische Briefe. Giessen, Germany, 1854.

twentieth century

Armstrong, David M. A Materialist Theory of the Mind. London: Routledge and Kegan Paul, 1968. A modern classic, first systematic exposition of central-state physicalism.

Carnap, Rudolf. "Psychologie in physikalischer Sprache" (1932–1933). Translated by Frederick Schick as "Psychology in Physical Language," in Logical Positivism, edited by A. J. Ayer. Glencoe, IL: Free Press, 1959. Epistemic materialism.

Eliot, Hugh. Modern Science and Materialism. London: Longmans, Green, 1919.

Feigl, Herbert. "The 'Mental' and the 'Physical.'" In Minnesota Studies in the Philosophy of Science. Vol. 2, edited by Herbert Feigl et al. Minneapolis: University of Minnesota Press, 1958. Identifies mental states with brain processes.

Feyerabend, Paul K. "Materialism and the Mind-Body Problem." Review of Metaphysics 17 (1) (1963): 49–66. Claims materialism is the only plausible view.

Hook, Sidney, ed. Dimensions of Mind: A Symposium. New York: New York University Press, 1960. Deals with the relations of mind, body, and machinery from many points of view.

Lewis, David K. "Psychophysical and Theoretical Identifications." Australasian Journal of Philosophy 50 (1972): 249–258.

Nagel, Ernest. "Are Naturalists Materialists?" In his Logic without Metaphysics. Glencoe, IL: Free Press, 1957.

Popper, Karl, and John C. Eccles. The Self and Its Brain. New York: Springer International, 1977. Full-scale attempt at a Cartesian dualism. Includes discussion of the argument from self-refutation.

Place, U. T. "Is Consciousness a Brain Process?" British Journal of Psychology 47 (1956): 44–50. Pioneering paper in central state physicalism.

Ryle, Gilbert. The Concept of Mind. London: Hutchinson, 1949. Readable and influential advocacy of analytic behaviorism.

Skinner, B. F. Science and Human Behavior. New York: Macmillan, 1953. Major statement of methodological behaviorism.

Smart, J. J. C. Philosophy and Scientific Realism. London: Routledge and Kegan Pual, 1963. Amplification of Smart's materialism.

Smart, J. J. C. "Sensations and Brain Processes." Philosophical Review 68 (1959): 141–156. Classic and influential pioneering physicalist paper.

Wittgenstein, Ludwig. Philosophical Investigations. Oxford: Blackwell, 1953. Influential but difficult reappraisal of the logic of mental concepts.

contemporary materialism

Braddon-Mitchell, David, and Frank Jackson. The Philosophy of Mind and Cognition. Oxford: Blackwell, 1996. Best modern introduction, with discussion of the qualia problem.

Chalmers, David J. The Conscious Mind: In Search of a Fundamental Theory. New York: Oxford University Press, 1996. Presents a moderate dualist position.

Churchland, Paul. A Neurocomputational Perspective. Cambridge, MA: MIT Press, 1989. Shows how information systems can exhibit mental powers.

Dennett, Daniel. Consciousness Explained. Boston: Little, Brown, 1991. Functionalist account of consciousness.

Gillett, Carl, and Barry Loewer, eds. Physicalism and Its Discontents. New York: Cambridge University Press, 2001. Sympathetic treatment of difficulties for materialism, with useful bibliography.

Jackson, Frank, ed. Consciousness. Aldershot, U.K.: Ashgate, 1998. Collection of articles, including some on qualia.

Kim, Jaegwon. Mind in a Physical World. Cambridge, MA: MIT Press, 1998.

Lycan, William G. Consciousness and Experience. Cambridge, MA: MIT Press, 1996. Functionalist view.

Lycan, Willaim G., ed. Mind and Cognition, An Anthology. 2nd ed. Malden, MA: Blackwell, 1999. Collection of influential articles.

Maxwell, Nicholas. The Human World in the Physical Universe: Consciousness, Free Will, and Evolution. Lanham, MD: Rowman & Littlefield, 2001. Presents a dual-aspect reconciliation of physical science and conscious experience.

McGinn, Colin. The Problem of Consciousness. Oxford: Blackwell, 1990. Argues the problem is beyond our competence to resolve.

Papineau, David. Philosophical Naturalism. Oxford: Blackwell, 1993. Concerns supervenience and physicalism.

Poland, Jeffrey. Physicalism; The Philosophical Foundations. Oxford: Clarendon, 1994. General and systematic presentation of the philosophy of materialism.

Post, John F. The Faces of Existence. Ithaca, NY: Cornell University Press, 1987. Propounds nonreductive materialism.

Rosenthal, David, ed. The Nature of Mind. New York: Oxford University Press, 1991. Collection of influential articles.

Searle, John. The Rediscovery of the Mind. Cambridge, MA: MIT Press, 1992. Antireductionist materialism.

Thau, Michael. Consciousness and Cognition. Oxford: Oxford University Press, 2002.

philosophical objections

Armstrong, David M. "Is Introspective Knowledge Incorrigible?" Philosophical Review. 72 (1963): 417–432.

Broad, Charlie Dunbar. The Mind and Its Place in Nature. London: Harcourt, Brace, 1925. Readable review of various doctrines of the mind.

Ducasse, Curt John. Nature, Mind, and Death. La Salle, IL: Open Court, 1951. Dualist attack on materialism.

Foster, John L. The Immaterial Self: A Defence of the Cartesian Dualist Conception of the Mind. London: Routledge, 1991.

Gunderson, Keith. "Descartes, La Mettrie, Language and Machines." Philosophy 39 (1964): 193ff. Revives argument from the generalized nature of reason.

Haldane, J. B. S. The Inequality of Man. London: Chatto and Windus, 1932. Presents the argument from self-refutation.

Haldane, J. B. S. "I Repent an Error." The Literary Guide. (April 1954): 7 and 29. Retracts argument from self-refutation.

Lewis, C. S. Miracles. New York: Macmillan, 1947. Expounds argument against materialism as self-refuting.

Paulsen, Friedrich. Einleitung in die Philosophie. 1892. Translated by Frank Thilly as An Introduction to Philosophy. New York: Holt, 1895. Idealist attack on materialism.

Plantinga, Alvin. "Probability and Defeaters." Pacific Philosophical Quarterly 84 (3) (2003): 291–298. Argues that materialism is self-subverting.

Keith Campbell (1967, 2005)