Physicalism is the idea that everything is matter. Idealism is the idea that everything is made up of a mental substance. Dualism claims that there are both matter and mind in the universe.

It appears a large portion of philosophy seems to be content with those two substances, and those three views. Are there philosophies that call for a third (or fourth) substance which is not matter nor mind? (phrased differently, any philosophies which define mind and matter such that there is something else that is neither)

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    Shouldn't this be tagged "reference-request"?
    – Philip Klöcking
    Commented Mar 6, 2016 at 17:38
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    @PhilipKlöcking Added. I'm not very good with the SE tagging system!
    – Cort Ammon
    Commented Mar 6, 2016 at 17:43
  • Platos world of Forms is a possibility; the Vedantic non-dualism posits another realm too. Commented Mar 6, 2016 at 23:15
  • The 'Perennial' philosophy or 'non-dualism' would be the most prominent case. It denies all forms of dualism and places the Ultimate beyond Mind and Matter. The psycho-physical world would be contingent and reducible to 'Unicity' or 'Brahman'. Dualism and Monism are rejected for non-dualism. .
    – user20253
    Commented Mar 29, 2020 at 15:13

5 Answers 5


The question refers to ontology. The classification matter or mind is a strong simplification.

Popper advocated a tripartition with

  • world 1: physical objects and events
  • world 2: mental objects and events
  • world 3: objective knowledge and ideas created by the human mind.

Popper describes his three worlds e.g., in Chapter P2, of Popper, Karl; Eccles, John: Das Ich und sein Gehirn. 1982 (Originally: The Self and its Brain. 1972).

Even for physics the concept of physicalism is to narrow when it is reduced to matter as basic concept. Since the days of Faraday and Maxwell the concept of field becomes increasingly important. Today it is discussed whether the field-concept is more fundamental than the matter-concept; e.g., whether particles are the excited states of a corresponding field.

Since the advent of computers it is discussed whether the classical concept of mind should be replaced by information. But until now neither mind nor information have found a precise and satisfactory definition.

Aside: I doubt that philosophy will advance when dealing with a dichotomy such simplistic and traditional like "mind or matter".

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    Your characterisation of Popper's "world 3" isn't really correct though; it's the world of ideas and concepts more generally, the things that the mind handles or produces. For example, Sherlock Holmes, or the notion of justice, belong to or exist in world 3. Commented Mar 6, 2016 at 11:56
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    @JoWehler Should the ontology tag be added to the question?
    – Insane
    Commented Mar 6, 2016 at 16:04
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    Thank you for the reference to Popper's theories. I need to do better research on him. I keep feeling like he keeps coming up with interesting ideas. Given that he's a dead philosopher, that tells me I need to research more =) As for your aside, I didn't want to put too much personal philosophy into the question, but I'm actually trying to remove the dichotomy completely by suggesting the question of whether the dichotomy exists does not need an answer. I'm comfortable with how it handles the traditional dichotomy, so I'm looking for test cases to push on it in ways I didn't think of.
    – Cort Ammon
    Commented Mar 6, 2016 at 17:27
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    Where does Popper say this in particular? Where is the mind - information replacement discussed?
    – Philip Klöcking
    Commented Mar 6, 2016 at 17:39
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    @Philip Klöcking Popper describes his three worlds e.g., in Chapter P2, of "Popper, Karl; Eccles, John: Das Ich und sein Gehirn. 1982 (Originally: The Self and its Brain. 1972)". - The necessity of a mind - information replacement is my claim.
    – Jo Wehler
    Commented Mar 6, 2016 at 17:56

It is very popular among philosophers to "overcome" the divide between idealism and materialism by dissolving the distinction, i.e. "embedding" both ideality and matter into something more fundamental, which they are then reconstructed as extreme cases of (equally popular is dissolving the distinction between subject and object). The idea is not to put a third option next to ideality and matter, but, to use Hegels's word, "sublate" them into a higher unity.

One of the first was perhaps Plotinus, the father of neo-Platonism, whose One precedes existence itself (and hence is neither ideal nor certainly material), and then "emanates" the world out of itself while remaining unchanged. This egress proceeds in decreasing phases of lucidity. The upper emanated echelons are ideas and ideal beings, while the lowest phase before the non-being is the inert matter. If this sounds familiar it should, Augustine and through him the Christian theology, was deeply influenced by Plotinus.

Spinoza accomplished it by dissolving God in nature understood as "being absolutely infinite, i.e., a substance consisting of an infinity of attributes, of which each one expresses an eternal and infinite essence... Extension is an attribute of God, or God is an extended thing". Material and ideal are simply different attributes perceived by us as disjoint due to a limited perspectives. What we perceive in the "physical progression" as causally moving matter is in the "logical progression" a chain of inferences about ideas (hard determinism follows). Spinoza was very optimistic, he believed in the "third kind of knowledge", unified grasping of the substance as a whole in all of its attributes. He claimed, the only one to do so in the West, that “the human Mind has an adequate knowledge of God's eternal and infinite essence”. In the East, similar ideas emerged much earlier in Vedic philosophies and religions, under the motto that Atman (soul) is identical to Brahman (world).

Kant, Husserl, Heidegger and so on would not stand to be classified so crudely as materialists, idealists or dualists either (they are also the ones who, along with Schelling and Hegel, claimed to dissolve the subject/object distinction). They redefine "matter" and "ideality" radically, both are treated not as constituents of reality, but more or less as different aspects of cognition. E.g. to Kant matter is the "blind" stuff of outer sensibility, without which ideas (concepts) are "empty". It makes little sense to talk about ideal and material separately, and no sense at all to apply such predicates to supersensible "things in themselves". Husserl's position is similar, he characterizes ideal and material as abstracted extremes of perceptual spectrum, with perception in its fullness fusing and surpassing both. Existentialists' "existence precedes essence" leads to a similar view.

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    Could you please name/quote work, chapter and/or page for these - as far as I can tell - correct statements in order to give a reference?
    – Philip Klöcking
    Commented Mar 6, 2016 at 17:43
  • @Philip Kant discusses matter e.g. in Amphiboly of Reflective Concepts in CPR, Husserl's account of sensation/ideation is in Eidetic Seeing (sec. I.3 of Ideas I). I described Plotinus's Enneads and Spinoza's Ethics from memory, but they are summarized in many phil history books. You may find Kant's second hand account of Spinoza interesting in §73 of CJ, it feeds directly into the discussion of that "intellectus archetypus" in §77.
    – Conifold
    Commented Mar 8, 2016 at 2:12
  • +1 I'd just say that Plotinus was not the first. This goes back the Upanishads, the Buddha, Lao Tsu and beyond. . .
    – user20253
    Commented Mar 29, 2020 at 15:15

Neutral monism holds that reality is neither mental nor material, but that mental and material properties arise from something else which is neither.


Well many monotheistic philosophies regard both (the human) mind and matter as created entities, while God himself is uncreated and hence cannot be either mental or physical entities. Some of these philosophers attempt to go further and 'explain' God as having divine essence, while some others insist that we cannot know what God's nature is.

Simply put, there are far more types of philosophies than just materialism or idealism or dualism. Even in ancient history some philosophers thought that everything was made of 4 elements, earth, air, water and fire. It may seem ridiculous in the light of modern knowledge, but some of them proposed that things that are composed of only a single element are divine, while those that are composed of more than one element are not divine. Others proposed that the 4 elements are not enough and there is a fifth called aether, sometimes even said to be the essence of the gods themselves (the Greeks had a pantheon).

I feel like pointing out that such concepts and terminology arise naturally from humans' tendency to attempt to find patterns where there are none. That explains why people gravitate towards such philosophies that 'conveniently' categorize everything into a few types, the 'best' being two as in dualism. Observe that dualistic ideas do not just come up in philosophical opinions on the human mind, but also in opinions on the structure of the world. In Taosim there cannot be good without evil, light without darkness, heat without cold, life without death, divinity without humanity, ... From science we do know that these are wrong (except the first and last ones which are not scientific claims). For instance darkness is simply absence of light, not an opposing entity, and cold is the absence of heat. There are even certain species that are immortal, contradicting the popular notion that life cannot exist without an inevitable biologically natural death (not due to accident or injury).

  • @sumelic: That is true for life as we know it, but how do you know for sure it is always true? Also, usually people have quite narrow views about life and death which don't even leave room for biological immortality, so that's an interesting thing to know.
    – user21820
    Commented Mar 6, 2016 at 18:31
  • @sumelic: I didn't intend that sentence to convey that meaning. I just intended it to mean that it contradicted popular conceptions of life and death and the associated claim as interpreted by most people. I've edited to clarify that; thanks!
    – user21820
    Commented Mar 6, 2016 at 18:40

Post-Lacan, a lot of psychoanalytic thought, even that which would openly disown him, has come to involve three layers of reality that are interlinked, but to some degree independent of one another -- the real, the ideal and the symbolic. These reside in the material, mental and cultural realms, respectively. (They have deeper historical psychoanalytic roots in the notions of neurotic movement 'from', 'against' or 'toward' in Horney. But Lacan gave them independent footing and an entirely different use.)

There is a temptation on the part of dualists to re-tread back from Lacan into Jung and consider the symbolic to be unconscious ideal material. But that makes it very hard to consider how it can be both personal and collective in nature, or how it does not, in fact, lose its force when it is discussed consciously, in the way that classically repressed ideas should.

Symbolism is intersubjectively established, so it cannot exist without interaction within the material realm between people with differing mental contents. It needs a material cue, but it resides spread across minds, in a culture, so it cannot be collected up as a mental object. Without some spooky sort of Berkeleyan or Hegelian "Overmind of God", you need a third category of being to account for our human structure as social animals and our dependence upon cultural contents.

It is also tempting to discount it as unnecessary category representing a combination of the other two. But our new awareness of the depth of 'Sapir-Worf' effects, and the degree to which humans are dependent upon language for thought implies that thought is not logically prior to symbolization. If symbolization is prior to thought, then, so is material, and there is either one, or three things going on, right from the beginning not two out of which the third arises.

(This seems to be, at base, @JoWehler's answer. Except that Lacan's ideas are both earlier and deeper than Popper's more 'positivistic' sudivision.)

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