There is a sharp distinction according to most commentaries between Berkeley and Kant - and perhaps it's purely due to the fact that Kant doesn't render experience in-itself enough to make sense of the manifold of sense-perceptions. However, I still do not understand why Kant even considers there might be a noumenal world which we do not possess ability to understand.

Why can't the reality structured by concepts of understanding and intuition just be pure ideas, as in the case of Berkeley (and this might be a poor caricature of Berkeley, but I hope I am clear about what I mean). I feel that if he even edges on accepting the possibility of there being no noumenal world at all, perhaps due to the un-knowability of it, his entire system would collapse. If all there is are ideas, then what's the distinction between concepts of understanding and sense-perceptions? All of the discourse would be rendered moot.

What's Kant argument for a world independent of our consciousness? Can he prove that it exists (even if it's totally different from our world of experiences)? And if it does, can he prove that it in fact plays a role in shaping our phenomenal world? If he can't do that, am I not right to assume that his entire critique is moot?

  • A hint : the very concept of "phenomenon" ( arguably) requires tha something is appearing. When you see a shadow projected on a veil , you are induced to think that the shadow is the shadow of something ( though you cannot know this somehing, due to the fact you cannot be directly presented with it).
    – user39744
    Commented Jun 3, 2020 at 14:07
  • There might be a distinction between the notion a " the noumenon" and the notion of a " noumenal world". The noumenal realm may not constitute a world properly.
    – user39744
    Commented Jun 3, 2020 at 14:09
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    That's exactly what Berkeley contested - the distinction between primary and secondary qualities. If I see a shadow, and I think of something that imparts that shadow - both are ideas. There's still no proof of their being actual matter. Commented Jun 3, 2020 at 15:08
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    There is no point for Kant to prove the existence of noumena because he is agnostic about them/it. All he says is that it is logically consistent to posit them. His system does not collapse from the unknowability of it, that unknowability is its basis. To the extent that he argues that noumena are distinct from phenomena it is from our deficient mode of knowledge about phenomena, discursive rather than holistic, intuitive. To know a thing as it is in itself is to create it, somewhat like to construct a triangle in imagination but beyond mere form, and we lack such divine power.
    – Conifold
    Commented Jun 4, 2020 at 4:18
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    His point is precisely to dismiss "anything real" in the old metaphysical sense, including Leibniz's and Berkeley's, as a product of confusion, and to reframe what we should concern ourselves with, namely the phenomena. While it is hopeless to keep guessing at the "real", we are in a much better position concerning our own cognitive apparatus and its deliverances, concepts, intuitions and experience. And there we have all the justification we need, because "justification" has a new meaning, one that matters, unlike the ephemeral aspirations of old metaphysics for "independent reality".
    – Conifold
    Commented Jun 4, 2020 at 8:41

2 Answers 2


I think your question arises from a misunderstanding of the conception of noumena in Kant. The noumenon (from nous, thought) is not an existing world out of reach. The thing in itself is a thought that has a methodological value, you could see it as a mental experiment, though this might be misleading. The whole idea is, as poorly as a few words can render it, that when considering all that can appear (i.e. all objects that can be given to a sensible intuition) as bound to the forms of our sensibility we are, logically, also cosnidering our thought as different from the objects that it thinks: the faculty that gives objects to thought isn't thought. Though that is clearly the case, at least the way Kant see's it, it isn't obvious that this is the only possible subjective order of faculties (i.e. we do not know the determining reason to account for such a subjective order of faculties). THis is exemplified by the possibility to think, though only in negative, of a different faculty, i.e. an intuitive intellect, that produces by itself his own objects of knowledge.

So: noumena is not a thing, (usually it is thought of as external thing, but that "external" makes the absurdity of the interpretation very clear, as it bounds it to the form of space). In asserting that my intellect is discoursive and it's objects are given to it by a sensible intuition I specularly determine a negative representation of a subject that has different faculties. How? By simply denying it my faculties. What is the definition of intuitive intellect? Well, that which is not discoursive, that which does not need a sensible intuition to provide objects: that which does not need judgment to gain knowledge. It's just part of the critical method, you need a restriction to account for the legitimacy of the assertion, that doesn't mean that you have to positi the existence of something out of those limits, moreover that is exaclty what Kant is trying to avoid, that we go on to determine something outside of the limits of possible experience.

If you think it through you will find that both denying and asserting the existence of noumena leads you to contradictions. There is a reason for that. Noumena is just the thought, unavoidable, of the non necessity of the faculties of the subject. I did not say contingency, and there is a reason, it's not something you can go on and search for it's determining reason. It's just a limit.

A subject with X faculties cannot account for his X faculties with his X faculties, for as soon as he considers that his faculties need a determining reason he considers them as contingent, hence every solution he can posit is going to be thought as bound to its own contingent faculties. Noumena is unavoidable for this very reason. It's just the rendering of a limit.

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    Are you saying that for Kant the noumena were distinguished by not being a product of "thought", but they could still be a product of a different aspect of mind, the "intuitive intellect", with no need to believe in any non-mind realities? If so, what about the fact that Kant included a "refutation of idealism" in the 2nd edition of the Critique, specifically attacking Berkeley? See muse.jhu.edu/article/227975/pdf
    – Hypnosifl
    Commented Jun 16, 2020 at 15:08
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    Also, in the introduction to the Cambridge edition of the Critique, p. 15 says that in the "Refutation of Idealism' section Kant "argues for the real existence of objects in space and time although for the transcendental ideality of their spatial and temporal forms". And p. 26-27 says that in an earlier 1755 work called the Nova dilucidatio, Kant had tried to furnish a proof of the "real existence of bodies", though it notes that in the Critique this argument is "changed from an ontological to an epistemological key".
    – Hypnosifl
    Commented Jun 16, 2020 at 15:20
  • You are in the right but the refutation of material or common idealism isn't the demonstration of the existence of noumena, it's the demonstration of the existence of the objects of external sense, i.e. not all that appears can be thought of as object of internal sense and so reception of the self. The refutation of material idealism is concerned with the distinction between internal and external, not between the distinction between sensible intuition and another possible intuition. As you quoted, Kant argues for the real existence of objects in space and time
    – Marc
    Commented Jun 17, 2020 at 8:32
  • The intuitive intellect is only a possible possibility (might be possible might be impossible, who knows) and as such is undetermined and undeterminable. THis has a relevance in establishing the limits of our knowledge. That noumenon can't be the object of knowledge means that our criterion of truth cannot be said to be a criterion of truth for all possible subjects but only for human ones.
    – Marc
    Commented Jun 17, 2020 at 8:35

Perhaps it's purely due to the fact that Kant does not render experience in-itself enough to make sense of the manifold of perception.

No. Kant took Humes discussion of sense perception and basically applied Platos ideas to it. He came up with a highly sophisticated schema of how consciousness itself forms and how it makes sense of the world that is presented to it. In other words, he turned Platos theory upside down, or rather inside out. This is why it's known as a variant of idealism. Everyone was doing it then, after all Marx turned Hegels ideas upside down too.

Given that Berkeley was espousing the traditional notions of Platonism its not surprising that there is a sharp distinction between them.

Moreover, given that he drained the noumena of all ideas - that is forms - it's not surprising he couldn't say very much about it.

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    This doesn't really answer the question of why Kant thought the postulate of the noumenal or thing-in-itself was necessary at all, why reality couldn't consist solely of conscious perception and thought as idealists like Berkeley believed. And Berkeley was not advocating traditional Platonism, he specifically denied the human mind could access independently-existing abstract ideas as discussed at jstor.org/stable/2708814 although he can be read as being favorably inclined to a neo-platonic view where abstract ideas exist in the mind of God (but he didn't explicitly advocate that)
    – Hypnosifl
    Commented Jun 3, 2020 at 20:54
  • I will just copy-paste the comment above: "if, however, I suppose that there be things that are merely objects of the understanding and that, nevertheless, can be given to an intuition, although not to sensible intuition (as coram intuiti intellectuali), then such things would be called noumena (intelligibilia). (A249)" This is a big IF. In my opinion if Kant cannot prove this IF, then his theory is just useless mental exercise. What does it matter if it's understanding or sense-experience if everything is given to us in 'ideas' - as if God caused it all in case of Berkeley. Commented Jun 3, 2020 at 21:31
  • @Hypnosil: Those questions weren't asked. Why don't you ask them if you are interested? Commented Jun 4, 2020 at 4:04
  • @MoziburUllah You answer doesn't answer my question which makes me quite confident you do not understand it - so it is quite ironical to say that my understanding of Kant is weak (which it probably is, and hence I came to this forum). That is not a defense of your unrelated answer. My question was that if Kant cannot prove the existence of a world independent of our consciousness, his theory is just a mental exercise - everything is an idea that exists inside of us (even sense-perceptions). Can you tell me what exactly about Kant did I not understand (THAT EXACTLY WAS MY QUESTION). Commented Jun 4, 2020 at 8:28
  • Also I reservedly apologise if the question wasn't framed well enough. But as @Hypnosifl comment shows that he understood my question, I am inclined to think you were here to just flaunt your better knowledge of philosophy and not to address the question. Commented Jun 4, 2020 at 9:13

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