Subjective idealism is the monistic metaphysical doctrine that only minds and mental contents exist. It entails and is generally identified or associated with immaterialism, the doctrine that material things do not exist. Subjective idealism rejects dualism, neutral monism, and materialism.

Could/have philosophers develop special languages geared towards such a view of reality? In particular, ones that would meet Quine's criterion of ontological commitment after paraphrasing non-existent entities:

"A theory is committed to those and only those entities to which the bound variables of the theory must be capable of referring in order that the affirmations made in the theory be true."

My guess is that its semantic primes should consist of:

  • qualia: individual instances of subjective, conscious experience such as the redness of an evening sky, pain of a headache, the taste of wine, etc.
  • A pronoun like *I* to refer to one's self
  • Verbs such as *think*, *believe*, *know*
  • Adverbs such as: *now*, *before*, *after*

Objects (e.g. chair, table, etc.), other personal pronouns (you, he, etc.), matter and all the other things that do not really exist (in the view of subjective idealism) would be defined as paraphrases.

  • @Conifold Right. My mistake. So Berkeley's subjective idealism is not what I meant. I am probably closer to Fichte's.
    – Bob
    Commented Jan 6, 2019 at 10:19
  • It will not be much different, you just paraphrase other thinking subjects into phenomena. Husserl does that too under his epoche principle (for the purposes of phenomenology suspend all beliefs about the external world), so-called constitution of intersubjectivity. This is even called methodological solipsism, see Solipsistic and Intersubjective Phenomenology by Hutcheson, Fichte was a precursor of phenomenology.
    – Conifold
    Commented Jan 6, 2019 at 10:41
  • @Conifold It sounds like you have enough raw matter to make an interesting answer.
    – Bob
    Commented Jan 6, 2019 at 17:41
  • @Bob I think that is of little or no significance to incorporate a pronoun like "I", as I think in my opinion, that the content of the "I" is reducible to the first variable Qualia (Q). Same for the verb "Know" as it can be reduced to "Evident", "True" and "Believe" in a doxastic and deontic sense.
    – SmootQ
    Commented Jan 6, 2019 at 18:45
  • 1
    @SmootQ You seem to have more than enough matter to make an interesting answer.
    – Bob
    Commented Jan 8, 2019 at 18:05

2 Answers 2


A subjective idealist can use exactly the same language as anyone else. Hence Berkeley's maxim that we ought 'to think with the learned, and speak with the vulgar' (Of the Principles of Human Knowledge, §51).

The point is that our phenomenologically experience is the same whether we are subjective idealists or not. A subjective idealist can talk about bumping into a table just as correctly as you or I can. But while you or I would probably think and talk of the table as in some sense a physical, non-mental object or thing, a subjective idealist has a reductive analysis of the table in terms of sensations and perceptions. For the subjective idealist,'I bumped into a table', re-analyses as something like 'I encountered sensations of resistance when I had a certain set of perceptions'. The language of physical objects and of our encounters with them is unaltered ('we speak with the vulgar'); the concepts which inform that language are radically revised ('we think with the learned').

The subjective idealist's ontological commitments are different from those of the vulgar, since the s/idealist is committed to the actual existence of only minds and their ideas or contents. The vulgar's include all sorts of other things, crucially including non-mental objects, events, states of affairs. But the two can share a language.

Response to objection

An objection has been put from, to me, an unexpected angle and I'd like to respond to it. The objection is :

I would agree that a subjective idealist can use exactly the same syntax as anyone else, but not the same language. Indeed, a language is not only defined by its syntax but also by its semantics. And the semantics given by a subjective idealist will be different form the one by a materialist (as you point out). – Bob.

Highly provisionally I want to say that the Three Dialogues between Hylas and Philonous support my view. In the dialogues Berkeley ('Philonous') sets out his ideas and arguments on behalf of subjective idealism. Hylas, his opponent, understands all the ideas and arguments that Berkeley presses forward on behalf of subjective idealism. Philonous and Hylas have a common language with shared syntax and semantics.

There is claim and counter-claim, rejoinder and surrejoinder. The opponents understand each other perfectly well. If they did not, they could not disagree. Yet at no point either in presenting his standpoint or in defending it or in attacking Hylas does Berkeley use any language different from Hylas'. His complete philosophy of subjective idealism, including its ontological commitments, is disclosed and elaborated in the Dialogues - nothing is withheld from 'the vulgar'. Yet the entire process runs on a common language with shared syntax and semantics which includes no linguistic innovations by Berkeley.

I expect the response : 'But these are only dialogues written by Berkeley himself'. Yes, they are but there is nothing in them that could not have been said or written by Berkeley, a real person, to another real person, a de-fictionalised Hylas, purely within the limits of a common language with shared syntax and semantics - the very language that the dialogues use.

It does not, of course, follow that there aren't non-Berkeleian versions of subjective idealism to which the common language defence does apply. But I feel justified in basing myself on Berkeley since his works are the loci classici for subjective idealism.


There is a misunderstanding here. Monism is not the abandonment of dualism but a form of it. Schrodinger points this out when he comments 'As well as the painting there is the canvas on which it is painted'.

The view that only mind exists or only matter exists in usually called monism. However, in order to exist a phenomenon must stand-out from a background and this is two things. It would be logically impossible for only one thing to exist.

Hence subjective idealism is a form of dualism. In order to reject dualism and escape from it we would have to abandon all distinctions and divisions for a doctrine of Unity. The sufi sage Al-Halaj warns us that even the remark 'God is One' is dualism for it implies a separation with the testifier. If we do this then we arrive at Absolute Idealism or 'non-dualism'. In Indian religion and philosophy this is advaita (not-two). The use of the phrase 'not-two' is a careful and deliberate avoidance of any suggestion of Monism, the idea that the world can be reduced to a numerical one. The Unity spoken of in non-dualism is not a numerical quantity and is a rejection of dualism.

Thus mind-only and matter-only theories are not an abandonment of dualism but a lightly disguised form of it. This is indicated by the fact that neither idea works and few philosophers see either as being a solution. The Mind-Matter problem persists precisely because it is not easy to transcend dualism. It would be no solution to reify one and de-reify the other.

The only way to move on from dualism is non-dualism. This allows us to transcend the subject-object distinction and all division, distinction, number and form for a doctrine of Unity.

Thus Russell, a neutral monist, is opposed the views of Bradley, an Absolute Idealist, and while the former declares metaphysics incomprehensible the latter explains it. This is because Russell's 'monism' is in fact dualism, as it rather obvious given that it requires a multiplicity of neutral phenomena.

This debate is old and well-rehearsed. It is not necessary to follow it. If we try to do so we discover we cannot conceive of an Ultimate that is one thing since in order to do so we must conceive of a second thing. For materialism these two things are often Atoms and Void, for idealism it might be mind and mental events.

The distinction between monism and non-dualism becomes more clear when we consider that subjective idealism uses ordinary language while non-dualism requires a language of contradiction and paradox. So different are they that they cannot share a language.

Another way to reveal the problem of monism is to ask whether it falls foul of Russell's paradox. We find that problems of self-reference prevent us from 'axiomatising' set-theory on a monistic single set, just as we are prevented from doing so in metaphysics. The logic just doesn't work. To overcome this problem we would have to abandon mind-only and matter-only theories. Russell agreed that his colleague Spencer-Brown solved this problem in his book Laws of Form by the use of a calculus modelling the non-dual description of Reality and endorsing Absolute or Transcendental Idealism. His own monism ran smack into his own paradox and this would be why he couldn't axiomatise set-theory or metaphysics.

In summary, subjective idealism does not require a different language and is merely the mirror-image of materialistic monism, bringing with it the same terminal problems. Non-dualism is the complete rejection of dualism and it requires a non-ordinary technical language that is easy to spot. This is why the literature of mysticism is so often seen as paradoxical and, by those like Russell who do not investigate it, so often judged to be 'irrational' or uninterpretable. It is because it is not endorsing dualism.

If we want to do our own research we only need attempt to imagine that only one thing or substance exists. It cannot be done. The set of all sets cannot contain itself. Monism, like explicit dualism, must be either incomplete (non-reductive) or inconsistent (absurd). This would be why metaphysics is difficult. If dualism or monism worked it would be a whole lot easier.

  • Monism is NOT a form of Dualism, for Monism is a claim that there is only ONE substance (Either mind or body) , while Dualism is the claim that there are 2 substances (Mind AND Body). There are 3 types of monism that I know of at least, Idealism (and solipsism), Physicalism and Neutral Monism (which states that both mind and body are reducible to a more substantial entity). While Dualism has 4 flavors that I know of : Classical Dualism, Epiphenomenalism, Parallelism and Interactionism , Personally I hold a monist physicalist view, that only matter exists.(-1 is not from me.)
    – SmootQ
    Commented Jan 11, 2019 at 21:28
  • @SmootQ Since you believe that "only matter exists", this implies that for you qualia do not exist. Conclusion: you are a zombie ;-)
    – Bob
    Commented Jan 12, 2019 at 10:12
  • @SmootQ - I feel you are missing a subtlety, which is that it would be impossible for just one substance to exist. You should be able to work out why this is. For a start, space-time would have to exist. But the proof of the pudding is in the eating. Can you solve metaphysical problems? If not then your monism is not useful. Monism states, as you say, that just one substance exists, and right or wrong this is not a view that works in metaphysics.
    – user20253
    Commented Jan 12, 2019 at 12:56
  • @SmootQ - PS - If you examine the meaning of 'exist' you'll find that two things must exist in order for one thing to do so. A metaphysical theory has to explain existence, not make it fundamental or pull it like a rabbit from a hat.
    – user20253
    Commented Jan 12, 2019 at 12:58
  • @Bob , not necessarily if you define matter as anything that interacts with the natural world without breaking the laws of nature, i.e : Anything that is not an immaterial 'soul' that has free will, since this concept would mean the addition or subtraction of energy from the physical Universe (and this breaks the laws). I.e : energy, particles, quantum fields, consciousness (and Qualia) if it is produced by the brain, can all be considered a part of the material world. There are materialist philosophers, and clearly they know they are not zombies, and still materialism exists,you should think!
    – SmootQ
    Commented Jan 12, 2019 at 21:51

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