Materialism vs Idealism: The Difference, and Why It Started a Gang War

Last updated: November 3, 2026

Materialism is the view that matter is the basic reality and that minds depend on it; idealism is the view that mind, or ideas, are the basic reality and that the material world depends on them. That is the core difference, and philosophers have been fighting over it for about two and a half thousand years. Plato already described the dispute in his dialogue the Sophist as “a sort of war of Giants and Gods” over the nature of being, with one side dragging everything down to what can be touched and the other defending itself “out of an unseen world”.

So the meme is historically accurate. Someone calmly lays out the case for hard materialism to a group of idealists, and the screen announces that a gang war has started. The image is from Grand Theft Auto: San Andreas, where shooting at the wrong people in the wrong neighbourhood has the same effect. Plato’s version has rocks and oak trees instead of guns, and otherwise the choreography is similar.

Matter First or Mind First?

The difference between materialism and idealism is a disagreement about what comes first. Materialists say that matter is fundamental and that thoughts, feelings and consciousness are produced by it. Idealists say that mind is fundamental and that what we call matter is in some way a product of, or dependent on, mind.

Friedrich Engels gave a much-quoted version of the split in Ludwig Feuerbach and the End of Classical German Philosophy (1886). He called the relation of thinking and being “the great basic question of all philosophy”, and wrote that the answers split philosophers “into two great camps”: those who put spirit first belong to idealism, those who put nature first to materialism. Engels was a partisan of one camp, and his history is tidier than the real one. There are dualists, like Descartes, who think mind and matter are both fundamental; there are neutral monists, who think both come from something more basic; and there are many philosophers who reject the question as badly posed. As a first map it still does the job, which is why textbooks keep borrowing it.

A quick warning, since the word trips people up: philosophical idealism has nothing to do with having high ideals, and it does not say that reality is unimportant. It says that minds and their contents are what reality is ultimately made of, or at least what everything else depends on.

Materialism vs Idealism: Examples That Make the Difference Clear

Abstract definitions only go so far, so it helps to put the same everyday questions to both camps. The answers below are simplified, and each side contains rival schools, but they show where the line runs.

Notice what the table does not show: disagreement about facts. A materialist and an idealist can agree on every measurement a scientist will ever make, on the wavelength of the sunset and the electrical activity of the dreaming brain. They disagree about what those facts are facts about. That is why the dispute has lasted so long and why no experiment can end it. It is also why the meme’s gang war is so pointless and so hard to stop. Both gangs control the same streets. They just insist on different names for them.

The last row is where the modern argument lives. Most materialists today accept that consciousness is real and claim it is a brain process. Idealists such as the contemporary philosopher Bernardo Kastrup reply that the brain is simply what a mind looks like when observed from outside, and that treating matter as basic makes consciousness inexplicable. Whichever side you lean towards, the question has stopped being antiquarian. It is the one that keeps neuroscientists, philosophers and, increasingly, people building artificial intelligence awake at night.

Atoms, Forms and a Fight That Plato Wrote Down

In ancient Greece, the materialist position was set out most clearly by the atomists Leucippus and Democritus from the fifth century BCE onwards, and the opposing camp is usually traced, a little loosely, to Plato. The atomists held that everything is made of tiny indivisible bodies moving in empty space, and, as the Stanford Encyclopedia of Philosophy puts it, offered an account of the natural world that did not rely on purpose or design.

The most famous line attributed to Democritus survives only because later writers quoted it: “by convention sweet and by convention bitter … but in reality atoms and void” (fragment DK 68B9, in the translation cited by the SEP). Heat, cold and colour get the same treatment. Colours and tastes, on this view, are how arrangements of atoms affect us, not features of the atoms themselves. A related idea returns some two thousand years later in the distinction between primary and secondary qualities, first argued by Galileo in The Assayer (1623) and made canonical by Locke, although historians disagree about how much either owed to the ancient atomists.

Plato’s answer went in the opposite direction. For him the most real things are the Forms, unchanging and knowable only by thought, while the physical world is a world of change and imperfect copies. Strictly speaking that is realism about abstract objects rather than idealism, since the Forms depend on nobody’s mind, which is why the SEP entry on idealism treats Plato as a forerunner rather than an idealist in the modern sense. He ends up in the idealist camp because he ranks the invisible above the material.

In the Sophist, a visitor from Elea describes the two parties as armies. The materialists “literally grasp in their hands rocks and oaks” and insist that only what can be touched exists; their opponents defend themselves from above and break the materialists’ bodies into “generation and motion”. Between them, he says, there is “an endless conflict raging”. The visitor then proposes a test: perhaps being is whatever has the power to affect something or be affected by it. The chastened materialists accept it for want of a better offer, the friends of the Forms reject it, and the war goes on.

The Bishop, the Table and the Stone

The classic idealist of the English-language tradition is George Berkeley, an Irish philosopher and later Anglican bishop of Cloyne, who argued in A Treatise Concerning the Principles of Human Knowledge (1710) that physical objects exist only as perceived. His formula, in section 3, is “Their ESSE is PERCIPI”: for things like tables and apples, to be is to be perceived.

Berkeley’s argument starts from something that sounds harmless. When I say the table I write on exists, he asks, what do I mean beyond the fact that I see and feel it, or would if I were in the room? Take away colour, shape, hardness and all the other perceived qualities, and nothing is left over that I could even describe. Berkeley concluded that the idea of matter existing on its own, unperceived, is not false so much as unintelligible. This does not make the world disappear when you leave the room. Berkeley says that things not perceived by us exist in “the mind of some Eternal Spirit”, meaning God (section 6). The theology is doing real work in the system, which is why later idealists who did not share it had to find other ways to keep the furniture in place.

Samuel Johnson’s reply is one of the most quoted refutations in English letters, and one of the weakest. James Boswell reports in his Life of Johnson that in 1763, while they discussed Berkeley’s “ingenious sophistry” outside a church in Harwich, Johnson struck his foot against a large stone so hard that he rebounded from it, and said, “I refute it thus.” Satisfying, and on most readings beside the point. Berkeley does not deny that stones are hard or that kicking them hurts. He denied that there is anything to the stone beyond the hardness, the resistance and the pain, which is exactly what Johnson’s foot experienced. All Johnson showed was that the stone could be perceived, which was Berkeley’s point to begin with.

Kant’s Compromise and Hegel’s Empire

Immanuel Kant tried to end the war by redrawing the map. He called his position transcendental idealism and argued that space, time and the basic categories of thought are contributed by the mind, so that we know things only as they appear to us, never as they are in themselves.

He was also keen not to be confused with Berkeley. The SEP entry on Kant’s transcendental idealism states that transcendental idealism “is a form of empirical realism”: within experience, tables and stones are real objects in space, not private ideas in one person’s head. Berkeley appears in Kant’s work as the example of a “dogmatic” idealist, and the second edition of the Critique of Pure Reason (1787) added a short section called the “Refutation of Idealism”, which, the SEP notes, is line for line among the most thoroughly commented passages in all of Kant. More than two centuries later, Kant scholars are still arguing over which side he actually signed for.

Georg Wilhelm Friedrich Hegel turned idealism into a system of world history. On the traditional reading, his absolute idealism treats reality as a whole as the self-development of reason or spirit, unfolding through history. Hegel is one reason the next round of the fight became political, because a young man who had turned Hegelian as a student in Berlin later decided Hegel had everything upside down. For how that method works, see our post on Hegel and the dialectic.

Marx Turns Hegel the Right Way Up

When Marx called himself a materialist, he mostly meant something about history and society, not about atoms. His historical materialism claims that the way a society produces its material life shapes its law, politics and ideas, rather than the other way round.

The key sentence is in the preface to A Contribution to the Critique of Political Economy (1859): it is not consciousness that determines people’s existence, “but their social existence that determines their consciousness”. In the afterword to the second German edition of Capital (1873), Marx described his relationship to Hegel in a famous image. In Hegel, the dialectic “is standing on its head”, and it has to be turned right side up. Marx kept Hegel’s idea that history moves through conflict and contradiction and replaced the self-development of spirit with the development of production and class relations.

Marx and Engels sometimes get filed as “soft materialists” in the philosophy-of-mind sense. That mixes up two debates. The question in philosophy of mind is whether mental states are physical states; the question in historical materialism is whether economic conditions explain ideas and institutions. A person could accept one and reject the other. Later Marxist writers developed “dialectical materialism” as a general philosophy of nature, and how far that goes back to Marx himself, rather than to Engels and later Soviet philosophy, is a long-running dispute among scholars.

Why Materialistic Is Not a Philosophy

The everyday words “materialistic” and “idealistic” describe attitudes, not theories of reality. Someone materialistic cares about money and possessions; someone idealistic acts on principles and hopes for a better world. A philosophical materialist can be generous, and a philosophical idealist can be a miser.

Engels was already irritated by this mix-up in 1886, and his rant has aged well. In the same text on Feuerbach, he wrote that by “materialism” the philistine understands gluttony, drunkenness, cupidity, “profit-hunting, and stock-exchange swindling”, in short the vices he practises in private, while “idealism” means the belief in virtue and a better world that he professes in public. Engels blamed the bad reputation of the word partly on its defamation by the priests. You do not have to buy his anticlerical diagnosis to take the point: the metaphysical dispute is about what exists. Who picks up the dinner bill is a separate question.

The Twentieth Century: Idealism Falls, Then Comes Back in Strange Clothes

Around 1900 idealism was the dominant philosophy in British universities. Thinkers such as F. H. Bradley and J. M. E. McTaggart, drawing on Hegel, argued that reality is a single spiritual whole and that time, space and separate things are, in some sense, appearances. The revolt came from Cambridge. In 1903 G. E. Moore published “The Refutation of Idealism” in the journal Mind, and he and Bertrand Russell set out to replace grand systems with careful analysis of propositions. Russell later wrote that escaping idealism felt like escaping from a hot house onto a windswept headland. Within a generation, idealism had become a historical curiosity in English-speaking philosophy, and analytic philosophy grew up as a largely realist, increasingly materialist enterprise.

Moore’s argument went straight for Berkeley’s formula. In every sensation, he argued, we must distinguish two elements: the consciousness, which is the same whether I sense blue or green, and the object, blue or green, which differs. Once you separate the act of being aware from what you are aware of, there is no reason to think the object depends for its existence on the act. Esse is not percipi. Whether the argument really works is still disputed, and Moore himself later had doubts about details, but its effect was enormous. It made the idealist’s central move look like a confusion of grammar rather than a discovery about reality.

Then physics reopened the question from an unexpected direction. In The Nature of the Physical World (1928) the astronomer Arthur Eddington, the same Eddington whose eclipse expedition confirmed Einstein, wrote that “the stuff of the world is mind-stuff”. His argument was that physics tells us only about the structure of the world, the mathematical relations between measurements, and leaves its intrinsic nature blank. The only intrinsic nature we know directly is our own experience. Russell had made a similar point, and it is the ancestor of today’s panpsychism. Much later the physicist John Archibald Wheeler summed up a different strand with the slogan “it from bit”, the suggestion that physical things arise from information.

A word of caution is needed here, because popular science has done idealism no favours. Quantum mechanics is often said to show that consciousness creates reality, since measurement affects outcomes. Most physicists reject that reading: a measurement in quantum theory is a physical interaction, and a detector does not need to be conscious. Idealism does not need quantum mysticism to be interesting. Its best arguments are still the old ones from Berkeley and Kant, about what we can intelligibly say exists beyond experience, together with the new one from the hard problem of consciousness.

So Who Is Winning?

Among professional philosophers surveyed today, mostly in English-speaking departments, materialism in its modern form, usually called physicalism, is a narrow majority view, and idealism is a small minority. Consciousness is where the materialist side is weakest.

The 2020 PhilPapers Survey asked 1,733 philosophers in its target group about the mind: 51.9% accepted or leaned towards physicalism and 32.1% towards non-physicalism. On the external world, 79.5% accepted or leaned towards non-skeptical realism and 6.6% towards idealism. Metaphysics is not settled by a show of hands, but if you want to know where the profession stood in 2020, that is it.

The resistance comes from what David Chalmers in 1995 named the hard problem of consciousness. As the Internet Encyclopedia of Philosophy explains, a full physical account of the brain seems to leave out what it is like to be the subject having the experience. Reactions range from denying that there is a problem at all to accepting panpsychism, which the SEP defines as the view that mentality is fundamental and ubiquitous in the natural world, and which its supporters present as a middle way between physicalism and dualism. The same entry notes that panpsychism has recently enjoyed a revival in analytic philosophy, so the giants’ win looks less tidy than the survey numbers suggest, even if some of the new panpsychists insist they are still on the giants’ side.

Why “Hard Materialism” Starts the Shooting

“Hard materialism” is not a standard technical term, so the meme leaves some room. The most natural reading is a reductive or eliminative materialism: the view that mental states are nothing over and above brain states, or, in the eliminativist version, that some everyday mental concepts will not survive a mature science of the mind at all.

The SEP calls eliminative materialism “the radical claim” that common-sense psychology is deeply wrong and that some or all of the mental states it posits do not exist. You can see why idealists would reach for their weapons. To an idealist, being told that the mind is not what it seems from the inside sounds like a claim that undermines itself, because the telling, the hearing and the doubting are all happening in a mind. To a hard materialist, appealing to how things seem from the inside is exactly the habit that science has broken in field after field. Each side accuses the other of explaining away the very thing that needed explaining, and twenty-four centuries after the Sophist, no ceasefire is in sight.

For the other half of Marx’s famous inversion, read Hegel and the Concepts of Dialectic.