I'd like to put forward a lukewarm defence of Kant as a friend of science.

Kant is on board with the idea that common sense observations like "refrigerators exist", or a car has four wheels" are true... enough.. In context. He calls it "emprical realism". He summarises his system as "empirical realism and transcendental idealism". Not as "you can't know anything".

Empirical realism means perceptions are based on information entering the mind via the sense organs. Kant is in agreement with basic scientific realism on this point. He also emphasised the realist side of his philosophy by adding a "Refutation of Idealism" to the second version of the Critique of pure Reason.

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. We can concede that humans and bats perceive the world differently.. although Kant goes further than most.

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.

Why does Kant include Transcendental Idealism and not go for 100% realism? Because he is trying to rescue science from some philosophical criticisms! Berkely and other idealists attacked the occult, invisible nature of Newtonian gravity and absolute space. It seemed an embarassment for empirical science to be based on invisible things. Additionally, Hume attacked the cause-effect relation as indiscernable from mere temporal succession

Transcendental Idealism is a stepping stone to the central point of Kants system, the argument that space and time and causality and substance are categories that the human mind uses to organise its sense data, not external realities. He described this radical view with a term borrowed from science: a Copernican Revolution.

Kant was impressed by Newton's physics (and lectured on astronomy himself). He believed that nothing less than a necessary connection between cause and effect would do justice to Newton's clockwork determinism. His contemporaries were happy to accept that logical implications were necessary, but Hume had argued that fire did not imply smoke.

To meet this difficulty, Kant restructures the traditional logical/empirical distinction into a fourfold grid of analytical/synthetic times apriori/a posteriori, and places causality in the "synthetic apriori" quadrant. By any account, something is necessary if it true in all possible cases. Kant tries to restore the necessity of causality by arguing that cause and affect (and the other categories of transcendental idealism) must hold on all possible cases of human perception.

So the idealistic aspects of Kants are there to support the science of his day against sceptical attacks, and are accompanied by realistic elements.

Whether his strange and ingenious scheme is still necessary is very open to debate. Neither physical determinism nor logical necessity are as important as they were; our notion of empiricism includes a strong element of abduction, or influence to the best explanation; we end to have multiple theories rather than different paradigms; and we have become comfortable with invisible entities.

Nonetheless, some of Kant's ideas remain open question, for instance the ontological status of time.

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The reason I’m focusing on this is that I think some of the phrasings you chose in trying to summarize Kant (and translate or steelman his views) are sliding between the three different claims I described above:

[1] “We can’t know things about ultimate reality without relying on initially unjustified knowledge/priors/cognitive machinery.” [2] “We can’t know things about ultimate reality.” [3] “(We can know that) ultimate reality is wildly different from reality-as-we-conceive-of-it.”

With regard to Kant's claims, there is no "sliding" because he assert

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1TAG7moI can't see why equivocation is helpful. If you want to ascertain the existence of some kind of noumena, you need to distinguish the thing you can do -- come up with a theory of the causes of your perceptions as external physical things -- from the thing you can't do -- get outside the map entirely. The significant-sounding claim does indeed follow from the trivial sounding one. That makes it a good argument. Good arguments should draw non-obvious conclusions from well-founded premises.
2Rob Bensinger7moI 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):

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.