Berkeley asserts that it is meaningless to speak of things-in-themselves that are not subject to human evaluation. Given that, no ampliative judgements can be made by postulating a causal relation between the so-called noumenal and phenomenal realms. It seems that Kant would agree with Berkeley on the former point, but disagree on the latter. If Kant disagrees, then what are his reasons for doing so?

  • Just to clarify (it doesn't affect whether I will answer). Is this homework?
    – virmaior
    Apr 27, 2015 at 23:09
  • Hello. What is "human evaluation"? What are "ampliative judgments"? Apr 27, 2015 at 23:23
  • Is this the same Berkeley that said it was meaningless to speak of infinitesimals which provoked the invention of analysis with their dance of epsilons and deltas? Apr 28, 2015 at 0:00
  • Why would Kant agree with Berkeleys judgement that an essential part of his metaphysics is meaningless? Apr 28, 2015 at 0:53
  • Hey, virmaior, nope, it's not homework. I'm just struggling with working out Kant's metaphysics.
    – duskn
    Apr 29, 2015 at 0:08

1 Answer 1


I am not much of a Berkeley scholar so my answer will primarily be an attempt to explain Kant with reference to the things you state in your question.

I think we need to be very careful about what exactly we mean by

it is meaningless to speak of things-in-themselves that are not subject to human evaluation.

This sentence can have several different meanings, which may be creating a false sense of agreement between the positions of Berkeley and Kant. For Kant, the sentence:

We do not know about things in themselves

would be true. But that's no identical to "it is meaningless to speak ..." To understand why, we need to attend to what Kant means by "know" and "understand." For Kant, understanding is something we bring to our interaction with things. Or to state it more clearly. He thinks there are:

  1. Things
  2. Sensibles
  3. Objects

And that things when rendered under for the forms of sensibility (space and time) are sensibles for us. And then when subject to the apparatus of the understanding (which for him is 12 categories) become objects of our knowledge. In other words, Kant's claims about not being able to know things is an epistemic claim -- rather than a metaphysical one. In fact, it hinges on a metaphysics of understanding where such things do exist but are restricted from our knowledge precisely because the process of knowing makes them sensibles and then objects for us.

I take it that Berkeley's idealism is suggesting more of an Occam's razor regarding the metaphysical existence of things like things-in-themselves, i.e., if we cannot encounter them in our world of ideas, then we should not speak as if they exist.

A second potential point of confusion is that you're identifying things-in-themselves with noumenon. But this interpretation of Kant is problematic. phenomenon / noumenon is a pair of terms that refers to things-as-we-encounter-them and then on the side, certain types of things we cannot encounter, which seems to include the wills of other rational creatures, our own internal maxim, and other things that are not necessarily things-in-themselves.

Thus, we need to consider the second point where they disagree and how best to word that. Here, I want to focus on

by postulating a causal relation between the so-called noumenal and phenomenal realms.

There's (at least) two problems with this language for Kant and the Kantians. First, Kant does not think we postulate causal relationships; he thinks we impress these on sensibles as part of the act of understanding. Second, there is no causal relationship between noumenon and phenomenon in Kant's view, because causality is something we bring in understanding, and we don't understand noumenon.

In fact, this is part of the point. Morality lies outside of our understanding for Kant. We don't know how people behave morally since we do not have access to the rational will that can act outside causality -- either in ourselves or in others.

This, however, might not assuage your worries since we (or at least I) sure have been talking a great deal about things that I'm claiming Kant says we cannot know/understand. The trick is that Kant's philosophy is not about understanding alone -- but also about reason, which he takes to be our highest faculty. And we can through reason deal with things that we cannot understand, viz., noumenon and the structures that operate in metaphysics.

Will this convince the Berkeleyian or Humean? I doubt it. But for Kant, what we are doing when we talk about things-in-themselves is discussing something that reason proves is necessary to the process of understanding.

  • I am interested in Kant and I find your answer useful. Though, would you mind clarifying several points: 1. How reason operates? It seems that you are suggesting that in Kant's view, understanding and reason are of different level of epistemic function, while to me understanding is not a faculty but reason is, and if its so, what's the word suitable for the state of function of reason? 2. How can reason deal with noumenon? Is reason of noumenon too? I know it would be too demanding to explain here, so a few sources regarding my questions will already be largely appreciated. Thanks
    – Fatto Lee
    Apr 30, 2015 at 16:42
  • Thanks for a great answer, virmaior! Could you clarify as to what you mean by saying that 'reason proves is necessary to the process of understanding'? Does it mean that Kant holds that the things-in-themselves a Pure Category of Understanding? At least to me it seemed that only Categories + Sensibilia are necessary and jointly sufficient conditions for understanding. If so, how do the things-in-themselves fit into either Categories or Sensibilia? Thanks for your time
    – duskn
    Apr 30, 2015 at 23:10
  • Also, does the Reason actually prove anything in Kant? I thought it provides a heuristic for living a good life?
    – duskn
    Apr 30, 2015 at 23:13
  • @FattoLee - 1. how reason operates is several hundred pages of the Critique of Pure Reason and not especially necessary to answer the question asked by the OP. If you want to know, ask a new question. 2. Reason is noumenal. For Kant, noumenon are excluded from knowledge but are part of how we think.
    – virmaior
    May 1, 2015 at 0:35
  • @duskn things-in-themselves are not categories of the understanding. For Kant, understanding requires that there is a thing (metaphysical claim) which we then place under the forms of sensibility and categories of understanding (epistemic activity). Things-in-themselves "fit into" the schema as the things that we apply space/time (forms of sensibility) and then the twelve categories to. As such, they are not identical to either categories (which are in our minds whose application makes objects) or sensibilia (which are things we have rendered under the forms).
    – virmaior
    May 1, 2015 at 0:38

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