I know of one answered question on a similar subject, but mine is not quite the same thing.

Berkeley's idealism holds that to be is to be perceived---nothing can exist, or can be thought to exist, without something perceiving it. An unperceived thing is literally inconceivable. The world remains extant when we're not looking because God is looking, all the time. We get to keep our idea of a permanent world, and multiple people living in it, by this move.

Kant's (considerably softer) idealism holds that we only have access to phenomena, but we know noumena absolutely must exist. I'm not solid on this bit, but phenomena are sort of "wrapped around" noumena? Causality is a property of phenomena, but phenomena in some way spring from noumena. Maybe noumena are the material substrate Berkeley rejects? In any case we somehow get to have a permanent world, and multiple people living in it.

I'm not sure if anyone notable subscribes to this view, but a third option, solipsism, is that there is nothing ensuring the permanent existence of things, and the world really does stop existing when we're not looking, and nobody else has any subjective experience.

My question is, is there any kind of fourth option? Is there any way to be an idealist without believing that the world is only sustained by God watching it, and also denying (or, like Berkeley, finding incoherent) the idea of noumena or a material substrate? And can we hold this belief without falling into solipsism?

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    Kant's noumena are reason's "completions" of our experience that condition the possibility of systematic knowledge, an illusion reason can't help but fall into, not something that "absolutely must exist". The kind of (metaphysical) reasoning that leads to concluding that such conditions "must exist" Kant characterizes as fallacious application of "categories of experience beyond any possible experience". Is objective idealism what you are looking for (Plato, Leibniz, more recently Peirce and Whitehead)?
    – Conifold
    Commented Feb 16, 2017 at 19:59
  • I think maybe it is---when the Wikipedia page says in an important sense there is only one perceiver, what does that mean for other minds? Are we all just fragments of the same consciousness, or is there only me?
    – Canyon
    Commented Feb 16, 2017 at 20:46
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    Wikipedia is screwing it up a bit, the more traditional description is given later "Idealism, in terms of metaphysics, is the philosophical view that the mind or spirit constitutes the fundamental reality", or more precisely, that the "fundamental reality" is more like mind than matter. There is no limit on the numbers of perceivers, or requirement that the constituents of reality be "conscious" (Plato's Ideas aren't), let alone pieces of one consciousness. A unifying "superconsciousness" is more a feature of what is called "absolute idealism".
    – Conifold
    Commented Feb 16, 2017 at 21:04

2 Answers 2


There is a fourth option and it's called 'nondualism'. This is the 'Absolute Idealism' of Francis Bradley. For this form of idealism solipsism would be not strictly false or true, and there would be no ultimate noumenon. For this view (contra to Kant), the Ultimate would be a phenomenon but (uniquely) it would have no associated noumenon.

A noumenon would have no distinguishing features so there can only be one. All phenomena would share the same noumenon or 'ground-of-being' and always the same one. This would be consciousness. But this word 'noumenon' is not usually used because it is inappropriate.

The phrase 'Monistic Idealism' has been mentioned. This may be the same view, but it seems best avoided to me since nondualism is not monism except by a very specific definition of 'monism' so the use of the latter word can lead to misunderstandings.

I have an essay under review on this topic if you'd like to read it. The issue you ask about is how Kant's 'noumenon' relates to Nagarjuna's 'emptiness'. There are crucial differences but their common features makes them worth comparing and contrasting. Roughly, the 'thing-in-itself' would contain and comprise all phenomena, making solipsism in one sense true, and this would be the reason why we cannot falsify it.

  • Would it be correct to say that Bradley's position is ontologically identical to, but epistemically different from, Hegel's absolute idealism?
    – Philip Klöcking
    Commented Aug 27, 2017 at 12:08
  • @Philip Klocking I'm no Hegel expert but this seems possible to me. In fact the more I think about it the more I like the idea. Could you say a few words about what would make them epistemically different?
    – user20253
    Commented Aug 28, 2017 at 12:33
  • The unitary/monistic entity of noumenon would be (Welt-)Geist, which in its self-differentiation (and self-realisation) can be known through speculative reason sublating (phenomenal) differences. The main difference to Kant is the emphasis on actually being able to know the ultimate being as it is, i.e. a unitary consciousness differentiating and realising itself, thereby producing all the phenomenal differences we call experience. At the same time, they are real as realisations of it and known correctly. And I have the feeling that is something Bradley would refuse to commit to.
    – Philip Klöcking
    Commented Aug 28, 2017 at 13:52
  • @Philip Klocking - Got it, thanks. This makes sense to me. Kant slipped up in a couple of ways imho, by making his 'thing-in-itself' plural and by making it unknowable. But it's tricky, since when we transcend the 'knower-known' distinction we transcend knowing. Kant doesn't allow for the sort of unknowing that is pure identity. Shame he wasn't able to read the Upanishads. Anyway, I'd agree with your point.
    – user20253
    Commented Aug 29, 2017 at 10:55
  • Btw, historically interesting in this respect is Judgement and Being by Friedrich Hölderlin, who in 1795 put emphasis on the inherent incompatibility of unity and knowledge, i.e. that every judgement implicitly includes the division of object and subject and in Being, they are indifferent and therefore there's no knowledge of Being. Basically Kant plus Spinoza.
    – Philip Klöcking
    Commented Aug 29, 2017 at 11:02

Dr. Amit Goswami puts forth a thesis of Monistic Idealism in his book, The Self-Aware Universe: How Consciousness Creates the Material World, 1993. He holds that consciousness is the bases of all reality and that it is a fundamental part of everyone. This makes his paradigm free from solipsism.

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