Re "was Berkeley making such an obvious mistake?", I think this is historians' majority view, but multiple people have tried to come up with more reasonable versions of the argument; see Gallois (1974) and Downing (2011). Note that Berkeley makes the same argument in dialogue form here (starts at "How say you, Hylas, can you see a thing which is at the same time unseen?"), so you can check if you find that version more tenable.

The Bloomsbury Companion to Berkeley says:

[This passage] can be interpreted as making a straightforward howler, arguing that because whenever you think of something it is being thought of and anything being thought of is, ipso facto, 'in the mind' then you cannot think of something that is not in the mind. According to Russell, this was a keystone for idealism and it involves a simple mistake.

"Berkeley's view . . . seems to depend for its plausibility upon confusing the thing apprehended with the act of apprehension. Either of these might be called an 'idea'; probably either would have been called an idea by Berkeley. The act is undoubtedly in the mind; hence, when we are thinking of the act, we readily assent to the view that ideas must be in the mind. Then, forgetting that this was only true when ideas were taken as acts of apprehension, we transfer the proposition that 'ideas are in the mind' to ideas in the other sense, i.e. to the things apprehended by our acts of apprehension. Thus, by an unconscious equivocation, we arrive at the conclusion that whatever we apprehend must be in our minds."
1912/1967,22

Russell's criticism is in line with Moore's famous 'The Refutation of Idealism' (1903), where he argues that if one recognizes the act-object distinction within conscious states, one can see that the object is independent of the act. This 'discovery', together with the development of a formal logic for relations, was the cornerstone of the rejection of 'British idealism'. If objects can be conceived of as independent of conscious thought, and if it is consistent to think of them as in actually related to each other, the mentalistic holism that was contemporary idealism is demolished.

That said, I put a lot of weight on Allen Wood's view as a leading Kant scholar, and revisiting his book Kant, he doesn't think Kant accepted the master argument (p. 69). David (2015) asserts a link, but it looks tenuous to me.

Kant's earliest interpreters took him to be saying "trees, oceans, etc. all just exist in your head and have nothing in common with the mysterious ineffable things-in-themselves", and Kant definitely talks like that a great deal, but he also says a lot that contradicts that view. Wood thinks Kant was just really confused and fuzzy about his own view, and didn't have a consistent model here (pp. 63-71).

My new pet theory is that Kant was being pulled in one direction by "wanting to make things as subjective as possible so he can claim more epistemic immediacy and therefore more immunity to skeptical arguments", and in the opposite direction by "not wanting to sound like a crazy person like Berkeley", so we get inconsistencies.

I don't know who, if anyone, noted the obvious fallacy in Berkeley's master argument prior to Russell in 1912, and Russell seems to think the argument was central to idealism's appeal. Regardless, my new view is: philosophy mainly ended up going down an idealist cul-de-sac because Kant shared Berkeley's "try to find ways to treat more things as subjective" approach to defeating skepticism. (Possibly without realizing it; Stang (2016) suggests Kant was pretty confused about what Berkeley believed.) Then Kant and Hegel built sufficiently dense, mysterious, and complicated intellectual edifices that it was easy for them to confuse themselves and others, while still being brilliant, innovative, and internally consistent enough to attract a lot of followers.

A simple sketch of how realism became unpopular

by Rob Bensinger 3 min read11th Oct 201953 comments

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[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.

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