I agree that Kant thought of himself as trying to save science from skepticism (e.g., Hume) and weird metaphysics (e.g., Berkeley), and I'm happy you're trying to make it easier to pass Kant's Ideological Turing Test.

Transendental idealism means all specific human perceptions are moulded by the general form of human perception and there is no way to backtrack to a raw form. [...]
The kind of knowledge he says you can't have is knowledge of the thing in itself, which in modern terms would mean something like knowledge that is not relative to some conceptual framework or way of perceiving. Physicalism doesn't refute that in the least, because it is explicitly based on using physical science as its framework.

I have two objections:

(1) Physicalism does contradict the claim "there is no way to backtrack to a raw form", if this is taken to mean we should be agnostic about whether things are (really, truly, mind-independently) physical.

I assert that the "raw form" of an electron, insofar as physics is accurate, is just straightforwardly and correctly described by physics; and unless there's a more fundamental physical account of electrons we have yet to discover, physics is plausibly (though I doubt we can ever prove this) a complete description of electrons. There may not be extra features that we're missing.

(2) Modern anti-realist strains, similar to 19th-century idealism, tend to slide between these three claims:

  • "We can't know things about ultimate reality without relying on initially unjustified knowledge/priors/cognitive machinery."
  • "We can't know things about ultimate reality."
  • "(We can know that) ultimate reality is wildly different from reality-as-we-conceive-of-it."

The first claim is true, but the second and third claims are false.

This sliding is probably the real thing we have Kant to thank for, and the thing that's made anti-realist strains so slippery and hard to root out; Berkeley was lucid enough to unequivocally avoid the above leaps.

Quoting Allen Wood (pp. 63-64, 66-67):

The doctrine can even be stated with apparent simplicity: We can have cognition of appearances but not of things in themselves. But it is far from clear what this doctrine means, and especially unclear what sort of restriction it is supposed to place on our knowledge.
Some readers of Kant have seen the restriction as trivial, so trivial as to be utterly meaningless, even bordering on incoherence. They have criticized Kant not for denying that we can know 'things in themselves' but rather for thinking that the notion of a 'thing in itself' even makes sense. If by a 'thing in itself' we mean a thing standing outside any relation to our cognitive powers, then of course it seems impossible for us to know such things; perhaps it is even self-contradictory to suppose that we could so much as think of them.
Other readers have seen transcendental idealism as a radical departure from common sense, a form of skepticism at least as extreme as any Kant might have been trying to combat. To them it seems that Kant is trying (like Berkeley) to reduce all objects of our knowledge to mere ghostly representations in our minds. He is denying us the capacity to know anything whatever about any genuine (that is, any extra-mental) reality. [...]
I think much of the puzzlement about transcendental idealism arises from the fact that Kant himself formulates transcendental idealism in a variety of ways, and it is not at all clear how, or whether, his statements of it can all be reconciled, or taken as statements of a single, self-consistent doctrine. I think Kant's central formulations suggest two quite distinct and mutually incompatible doctrines. [...]
Some interpreters of Kant, when they become aware of these divergences, respond by saying that there is no significant difference between the two interpretations, that they are only 'two ways of saying the same thing.' These interpreters are probably faithful to Kant's intentions, since it looks as if he thought the two ways of talking about appearances and things in themselves are interchangeable and involve no difference in doctrine. But someone can intend to speak self-consistently and yet fail to do so; and it looks like this is what has happened to Kant in this case.

In particular, here's Wood on why Kant is sometimes saying 'we can't know about the world outside our heads', not just 'we can't have knowledge without relying on some conceptual framework or way of perceiving' (p. 64):

Kant often distinguishes appearances from things in themselves through locutions like the following: "What the objects may be in themselves would still never be known through the most enlightened cognition of their appearance, which alone is given to us" (KrV A43/B60). "Objects in themselves are not known to us at all, and what we call external objects are nothing other than mere representations of our sensibility, whose form is space, but whose true correlate, i.e. the thing in itself, is not and cannot be cognized through them" (KrV A30/B45).
Passages like these suggest that things existing in themselves are entities distinct from 'their appearances' -- which are subjective states caused in us by these things. Real things (things in themselves) cause appearances. Appearances have no existence in themselves, being only representations in us. "Appearances do not exist in themselves, but only relative to the [subject] insofar as it has senses" (KrV B164). "But we should consider that bodies are not objects in themselves that are present to us, but rather a mere appearance of who knows what unknown object; that motion is not the effect of this unknown cause, but merely the appearance of its influence on our senses; that consequently neither of these is something outside us, but both are merely representations in us" (KrV A387).

Whereas (p. 65):

In other passages, transcendental idealism is formulated so as to present us with a very different picture. [...] Here Kant does not distinguish between two separate entities, but rather between the same entity as it appears (considered in relation to our cognitive faculties) and as it exists in itself (considered apart from that relation). [...]
On the identity interpretation, appearances are not merely subjective entities or states in our minds; they do have an existence in themselves. The force of transcendental idealism is not to demote them, so to speak, from reality to ideality, but rather to limit our cognition of real entities to those features of them that stand in determinate relations to our cognitive faculties.

A simple sketch of how realism became unpopular

by Rob Bensinger 3 min read11th Oct 201953 comments


[Epistemic status: Sharing current impressions in a quick, simplified way in case others have details to add or have a more illuminating account. Medium-confidence that this is one of the most important parts of the story.]

Here's my current sense of how we ended up in this weird world where:

  • I still intermittently run into people who claim that there's no such thing as reality or truth;
  • a lot of 20th-century psychologists made a habit of saying things like 'minds don't exist, only behaviors';
  • a lot of 20th-century physicists made a habit of saying things like 'quarks don't exist, only minds';
  • there's a big academic split between continental thinkers saying (or being rounded off to saying) some variant of "everything is culture / perception / discourse / power" and Anglophone thinkers saying (or being rounded off to saying) "no".

Background context:

1. The ancient Greeks wrote down a whole lot of arguments. In many cases, we're missing enough textual fragments or context that we don't really know why they were arguing — what exact propositions were in dispute, or what the stakes were.

2. In any case, most of this is screened off by the fact that Europe's memetic winners were Christianity plus normal unphilosophical beliefs like "the sky is, in fact, blue".

3. Then, in 1521, the Protestant Reformation began.

4. In 1562, the Catholics found a giant list of arguments against everything by the minor Greek skeptic Sextus Empiricus, got very excited, and immediately weaponized them to show that the Protestant arguments fail (because all arguments fail).

5. These soon spread and became a sensation, and not just for being a useful superweapon. Plenty of intellectuals were earnest humanists used to taking arguments at face value, and found Sextus' arguments genuinely upsetting and fascinating.

I trace continental thinkers' "everything is subjective/relative" arguments back to a single 1710 error in George Berkeley:

[...] I am content to put the whole upon this Issue; if you can but conceive it possible for one extended moveable Substance, or in general, for any one Idea or any thing like an Idea, to exist otherwise than in a Mind perceiving it, I shall readily give up the Cause[....]
But say you, surely there is nothing easier than to imagine Trees, for instance, in a Park, or Books existing in a Closet, and no Body by to perceive them. I answer, you may so, there is no difficulty in it: But what is all this, I beseech you, more than framing in your Mind certain Ideas which you call Books and Trees, and the same time omitting to frame the Idea of any one that may perceive them? But do not you your self perceive or think of them all the while? This therefore is nothing to the purpose: It only shews you have the Power of imagining or forming Ideas in your Mind; but it doth not shew that you can conceive it possible, the Objects of your Thought may exist without the Mind: To make out this, it is necessary that you conceive them existing unconceived or unthought of, which is a manifest Repugnancy.

If I can imagine a tree that exists outside of any mind, then I can imagine a tree that is not being imagined. But "an imagined X that is not being imagined" is a contradiction. Therefore everything I can imagine or conceive of must be a mental object.

Berkeley ran with this argument to claim that there could be no unexperienced objects, therefore everything must exist in some mind — if nothing else, the mind of God.

The error here is mixing up what falls inside vs. outside of quotation marks. "I'm conceiving of a not-conceivable object" is a formal contradiction, but "I'm conceiving of the concept 'a not-conceivable object'" isn't, and human brains and natural language make it easy to mix up levels like those.

(I can immediately think of another major milestone in the history of European thought, Anselm's ontological argument for God, that shows the same brain bug.)

Berkeley's view was able to find fertile soil in an environment rife with non-naturalism, skeptical arguments, and competition between epistemic criteria and authorities. Via Kant and Kant's successors (Hegel chief among them), he successfully convinced the main current of 19th-century European philosophy to treat the idea of a "mind-independent world" as something ineffable or mysterious, and to treat experiences or perspectives as fundamental.

(Edit: G.E. Moore seems to think that everyone in the 19th century was making an error along these lines, but I now suspect Kant himself wasn't making this mistake; I think his main error was trying too hard to defeat skepticism.

I also don't think Berkeley's writing would have been sufficient to confuse Europe on its own; it's too lucid and well-articulated. The transition to Kantian and Hegelian versions of these arguments is important because they were much more elaborate and poorly expressed, requiring a lot of intellectual effort in order to spot the inconsistencies.)

My unscholarly surface impression of the turn of the 20th century is that these memes ("the territory is fundamentally mysterious" and "maps are sort of magical and cosmically important") allowed a lot of mysticism and weird metaphysics to creep into intellectual life, but that ideas like those are actually hard to justify in dry academic prose, such that the more memetically fit descendants of idealism in the 20th century ended up being quietist ("let's just run experiments and not talk about all this weird 'world' stuff") or instrumentalist / phenomenalist / skeptic / relativist ("you can't know 'world' stuff, so let's retreat to just discussing impressions; and maybe you can't even know those, so really what's left is power struggles").

Today, the pendulum has long since swung back again in most areas of intellectual life, perhaps because we've more solidly settled around our new central authority (science) and the threats to centralized epistemic authority (religious and philosophical controversy) are more distant memories. Metaphysics and weird arguments are fashionable again in analytic philosophy; behaviorism is long-dead in psychology; and quietism, non-realism, and non-naturalism at least no longer dominate the discussion in QM, though a lot of Copenhagen slogans remain popular.

The above is a very simple picture featuring uneven scholarship, and history tends to be messier than all that. (Ideas get independently rediscovered, movements go one step forward only to retreat two steps back, etc.) Also, I'm not claiming that everyone endorsed the master argument as stated, just that the master argument happened to shift intellectual fashions in this direction in a durable way.