Thoughts on External World Skepticism

Interview of Bryan Frances, done by Evgeny Loginov

1. In your view, does an external world exist as a collection of objects, states of affairs, or facts that are independent of perception, reason, and consciousness? Can we prove, justify, or rationally confirm the existence of the external world; if so, how exactly? Does overcoming skepticism regarding the external world hold any philosophical value or significance?

The external world existed a long time before there were any humans or aliens. If it’s “dependent” on human or alien perception, reason, or consciousness in any remotely interesting sense of “dependent”, then human or alien activity has had a backward causal influence of billions of years. I don’t think so.

Even now, with human mental activity happening, nothing but bad philosophizing suggests that the existence of the external world depends on human or alien mental activity. I don’t believe in magic. Now, if you want to slap a weird semantics on “dependent” so that “The external world depends on human or alien consciousness” comes out true, that’s fine. But I doubt that the subsequent thesis will be of any interest.

If I were a theist, then I might think the universe came into existence via God’s mental activity. That would mean the creation of the external world is straightforwardly dependent on consciousness, albeit a supernatural one. But that wouldn’t mean that the external world continuously relies on God’s mental activity for its existence. I’m not a theist, and if I were, I would be humble enough to realize I have no decent evidence regarding these issues, so I wouldn’t have any opinions on them.

Some people might say that what we’re really interested in, with (1), is whether the filing of the external world into certain categories is dependent on consciousness, perception, or reason. So, it’s not a question of the external world’s existence but of how it’s cut up into pieces.

Even so, I’m like most philosophers in thinking that the external world is cut up into various objects, those objects have various properties and relations to one another, and human or alien consciousness has nothing whatsoever to do with it. The properties of protons, stars, or quasars aren’t dependent in any way on any human or alien consciousness. No magic.

A more interesting possibility is that the existence and/or characteristics of the external world don’t depend on human, alien, or supernatural mental activity but they do depend on extremely primitive mental activity—because every object in the universe has mental characteristics. This is the idea behind panpsychism. Every bit of the external world depends on consciousness because, trivially, it depends on itself and at least some other objects, each of which has some degree of consciousness. I don’t think there’s any evidence that the mental characteristics in question are anything like our thoughts or feelings, but perhaps they count as mental anyway in some stretched sense. Philosophers of mind have explored this idea, with some endorsement.

As for the external world existing “as a collection of objects, states of affairs, or facts”, it’s difficult for me to see how that could be false, given that “object” is pretty flexible. Perhaps “event” or “gunk” (a weird term from analytic metaphysics) should have been added to the list.

Moving on to address the second question, I suppose “prove” and “justify” are pretty flexible, but under most meanings I think we cannot “prove” the existence of the external world. As far as “rationally confirm”, I think it has weak meanings so that I rationally confirm the existence of trees when I see one in ordinary circumstances, and I can then deduce “Since trees count as external, there’s an external world”. That sounds like rational confirmation of the external world.

So, I think that in any super interesting sense, no, we can’t prove or justify the existence of the external world. Many philosophers have gotten comfortable with this result, thinking it’s not a big deal, but I have not. I can prove the existence of two-headed snakes just by going on YouTube; and the inference from “There are two-headed snakes” to “There is an external world” is solid. So, one would think it’s easy to prove the existence of the external world. Philosophers rightly think this is a genuine puzzle.

For the final question, regarding overcoming skepticism about the external world, I have a mix of thoughts because I’m uncertain as to what “know” amounts to.

I suspect that “know” has a semantics that makes knowledge unimpressive on the evidence/reliable process side. That is, it doesn’t take much for a true belief to count as knowledge. The reason so many epistemologists think otherwise is due to a professional selection effect: philosophers don’t become epistemologists unless they think evidence and justification are really important. In contrast, I suspect that what really counts for the acquisition of knowledge is having a true belief; matters about evidence or warrant aren’t remotely as important. So, that thought inclines me to think that skepticism about the external world is false, since we have plenty of knowledge of external matters.

Let me try to explain this a little further.

Someone tells you that he has friends who are witches. You object that that’s silly, since there are no witches. But then he informs you that “witch” is synonymous with “a woman who is eccentric, is really into the dark arts, and identifies as a witch”. Pretend he is right: that’s what “witch” really means in contemporary English.

Since he convinced you of that linguistic matter, you now admit that in English, your friend’s remark “I have friends who are witches” is straightforwardly true even though there is no such thing as black magic. In effect, the term “witch” has a watered-down meaning so that it doesn’t take much for someone to count as a “witch”. It is watered-down compared to what you thought it was; it is a helluva lot easier to be a “witch” than you thought.

Similarly, someone might say that the term “knowledge” has a watered-down meaning so that it doesn’t take much for a belief to count as “knowledge”. Regarding what it means for it to be watered-down, the witch case is supposed to help.

So, I’m inclined to think we have knowledge of external affairs, mainly because the bar for such knowledge is pretty low. In order to have a belief that is justified enough for knowledge, it doesn’t take much. I go over these issues in chapter 1 of Can We Know Anything?, co-authored with Michael Huemer, Routledge Press, 2023.

2. What do you think about G.E. Moore’s proof of an external world and, more broadly, the Moorean counterarguments against skepticism?

Here is one way to make the Moorean Move precise enough to evaluate:

When confronted with a deductively valid argument against P (e.g., P = “Jo knows there are trees”), the Moorean thinks that there is much more justification for P than there is for the conjunction of the premises in the argument against P. So, she concludes that it’s highly probable (but not guaranteed) that at least one of the premises is false—even if she hasn’t bothered to figure out which one is false, or why it’s false.

Let’s say that the Moorean move fails when it’s not true that the justification for P is much stronger than the justification for the conjunction of the premises in the argument against P.

I think there are plenty of occasions in which the Moorean Move is highly reasonable. For instance, there’s a famous “proof” that the sum of positive integers is -1/12. It’s reasonable to conclude that there’s a false premise somewhere, even if one has no idea where it is.

For the most part, I think philosophers overestimate the epistemic significance of common sense. Many beliefs are highly commonsensical but I don’t think that means that all or most of them have loads of justification—or, more to the point, a lot more justification than premises in some anti-commonsensical arguments. Roughly put, to be commonsensical, the belief has to be practically useful, but the connection between practical usefulness and justification isn’t as tight as most of us think. The Sorites paradox, the Liar and other semantic paradoxes, the Problem of the Many, and the material composition paradoxes all show that many commonsensical beliefs are false, even if we haven’t figured out which ones (see my The Epistemic Consequences of Paradox, Cambridge University Press, 2022). Similar remarks use not philosophy but physics.

So, I’m not impressed with the Moorean Move applied to deductive skeptical arguments. And even if they didn’t fail in the sense described above, they do nothing at all to tell us which skeptical premise is false or why. So even if the Moorean Move is successful, we still have to probe the skeptic’s argument to figure out where it goes wrong. Given that we have been doing that for centuries, with no stable consensus resulting, this particular Moorean Move seems unwise to me.

3. Consider the statement, ‘There exists some planet N, located beyond the observable universe (in such a way that the existence of this planet is fundamentally impossible to confirm or refute empirically, either now or in the future), and on N there is silver’. Can this statement be considered meaningful, or is it merely a nonsensical collection of words? Does this statement possess a truth-value (i.e., either it is true or it is false), given that it cannot be empirically confirmed or refuted?

I don’t think there’s any question that it’s a meaningful sentence. It consists of perfectly good words put together to make a declarative sentence that I understand just fine. In that way, it’s similar to the famous Chomsky sentence “Colorless green ideas sleep furiously”: of course we understand its meaning just fine.

Think about “Colorless green ideas don’t exist” and “Nothing sleeps furiously”. Those are true, but in order for them to be true, they have to be meaningful. So, both “colorless green ideas” and “sleeps furiously” are actually meaningful. So, put them together and you get . . . “Colorless green ideas sleep furiously”.

Under a natural reading R1, the Chomsky sentence is saying that every colorless green idea sleeps furiously. Alternatively, on closely related reading R2 it’s saying that the vast majority of colorless green ideas sleep furiously. On reading R3 it’s saying that the typical or generic colorless green idea sleeps furiously. Since there aren’t any colorless green ideas, the Chomsky sentence is kind of like “People with ten heads sleep furiously” or “My brothers live in Iran” (I don’t have any brothers). In order for the Chomsky sentence to be false, under any of the three interpretive ideas R1-R3, there would have to be a colorless green idea that doesn’t sleep furiously. Since there aren’t any colorless green ideas that don’t sleep furiously (because there aren’t any at all), the sentence isn’t false. It’s true.

Alternatively, one might think that the Chomsky sentence has a false presupposition, namely, that there are colorless green ideas. Since the sentence has a presupposition, and that presupposition is false, they say that the sentence itself is not true. But even then, we know all this in part because we know the meaning of the Chomsky sentence.

I understand that question (3) is probably trying to get at some other notion of meaning, so the above reflections might be beside the point. But I don’t know what that other notion is.

4. Is skepticism about the external world exclusively a product of Early Modern European philosophy, or does it possess universal relevance?

I don’t know.

5. How do interpretations of quantum mechanics that posit consciousness as a factor in wave function collapse influence debates about the independent ontological status of the external world?

I have a Master’s degree in physics and I know full well that I’m ridiculously underqualified to have an opinion on that matter. It would be best to ignore what epistemologists say in response to that question. I would ask some of the very few people in the world who know a great deal about the philosophical issues of quantum mechanics and who are great at philosophy as well, such as Tim Maudlin.

But I can’t help myself: how on Earth are my perceptions supposed to be factors in wave function collapse? If I look at a tree, which wave functions am I collapsing? Just one? Or trillions every second? There are many simple questions here that I never see even articulated, let alone reasonably answered.

6. What is your stance on the simulation hypothesis, the idea that our world is a computer-generated construct?

I cowrote a book on skepticism, so you would think I would have something intelligent to say in response to this question. Alas, life is short and my interests in skepticism have pretty much run out! I have various things I’m strongly tempted to say in response to (6), but since I know they will be amateurish, I don’t make them public.

7. What texts would you recommend as essential reading on skepticism about the external world?

For a book I’d recommend Barry Stroud’s The Significance of Philosophical Scepticism, Oxford University Press, 1984. For articles, I would go with some of the entries in the online Stanford Encyclopedia of Philosophy, especially those for “Skepticism”, “Epistemic Closure”, “Transmission of Justification and Warrant”, and “Epistemic Contextualism”.

If you want the best book ever, then of course the book I cowrote with Michael Huemer is the obvious choice: Can We Know Anything?, Routledge Press, 2023.