I mean "But we should consider that bodies are [...] 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" seems pretty unambiguous to me. Kant isn't saying here that 'we can only know stuff about mind-independent objects by using language and concepts and frameworks' in this passage; he's saying 'we can only know stuff about mere representations inside of us'.

Kant passages oscillate between making sense under one of these interpretations or the other (or neither):

  • the "causality interpretation", which says that things-in-themselves are objects that cause appearances, like a mind-independent object causes an experience in someone's head. If noumena are the "true correlates" of phenomena, while phenomena are nothing but subjective experiences, then this implies that we really don't know anything about the world outside our heads. You can try to squirm out of this interpretation by asserting that words like "empirical" and "world" should be redefined to refer to subjective experiences in our heads, but this is just playing with definitions.
  • the "identity interpretation", which says that things-in-themselves are the same objects as phenomena, just construed differently.

Quoting Wood (66-67, 69-70):

Yet the two interpretations appear to yield very different (incompatible) answers to the following three questions:
1. Is an appearance the very same entity as a thing in itself? The causality interpretation says no, the identity interpretation says yes.
2. Are appearances caused by things in themselves? The causality interpretation says yes, the identity interpretation says no.
3. Do the bodies we cognize have an existence in themselves? The causality interpretation says no, the identity interpretation says yes.
[... N]o entity stands to itself in the relation of cause to effect. Transcendental idealism is no intelligible doctrine at all if it cannot give self-consistent answers to the above three questions. [...]
Kant occasionally tries to combine "causality interpretation" talk with "identity interpretation" talk. When he does, the result is simply nonsense and self-contradiction:
"I say that things as objects of our senses existing outside us are given, but we know nothing of what they may be in themselves, cognizing only their appearances, that is, the representations which they cause in us by affecting our senses. Consequently, I grant by all means that there are bodies outside us, that is, things which, though quite unknown to us as to what they are in themselves, we still cognize by the representations which their influence on our sensibility procures us, and which we call bodies, a term signifying merely the appearance of the thing which is unknown to us but not the less actual. (P 4:289)
The first sentence here says that objects of the senses are given to our cognition, but then denies that we cognize these objects, saying instead that we cognize an entirely different set of objects (different from the ones he has just said are given). The second sentence infers from this that there are bodies outside us, but proceeds to say that it is not these bodies (that is, the entities Kant has just introduced to us as 'bodies') that we call 'bodies', but rather bodies are a wholly different set of entities. Such Orwellian doubletalk seems to be the inevitable result of trying to combine the causality interpretation with the identity interpretation while supposing that they are just two ways of saying the same thing. [...]
Kant of course denies that we can ever have cognition of an object as it is in itself, because we can have no sensible intuition of it -- as it is in itself. But he seems to regard it as entirely permissible and even inevitable that we should be able to think the phenomenal objects around us solely through pure concepts of the understanding, hence as they are in themselves. If I arrive at the concept of a chair in the corner first by cognizing it empirically and then by abstracting from those conditions of cognition, so that I think of it existing in itself outside those conditions, then it is obvious that I am thinking of the same object, not of two different objects. It is also clear that when I think of it the second way, I am thinking of it, and not of its cause (if it has one). From this point of view, the causality interpretation seems utterly unmotivated and even nonsensical.
The problem arises, however, because Kant also wants to arrive at the concept of a thing existing in itself in another way. He starts from the fact that our empirical cognition results from the affection of our sensibility by something outside us. This leads him to think that there must be a cause acting on our sensibility from outside, making it possible for us to intuit appearances, which are then conceived as the effects of this cause.
Of course it would be open to him to think of this for each case of sensible intuition as the appearance acting on our sensibility those a wholly empirical causality. But Kant apparently arrived at transcendental idealism in part by thinking of it as a revised version of the metaphysics of physical influence between substances that he derived from Crusius. Thus sensible intuition is sometimes thought of as the affection of our senses by an object not as an appearance but as a thing in itself, and transcendental idealism is thought of as having to claim (inconsistently) that we are to regard ourselves (as things in themselves) as being metaphysically influenced by things in themselves.
Such a metaphysics would of course be illegitimately transcendent by the standards of the Critique, but Kant unfortunately appears sometimes to think that transcendental idealism is committed to it, and many of his followers down to the present day seem addicted to the doctrine that appears to be stated in the letter of those texts that express that thought, despite the patent nonsense they involve from the critical point of view. The thing in itself is then taken to be this transcendent cause affecting our sensibility as a whole, and the appearance is seen as the ensemble of representations resulting from its activity on us.

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.