Belief Revision: Part 1

GE Moore was famous for refuting skepticism concerning the external world by raising each of his hands in turn and saying “here’s one hand, and here’s another.”[i] But most philosophers don’t take the project of refuting global skepticism very seriously.[ii] They might offer arguments to rebut or refute it, or they might not.  Why?  Skepticism of this radical kind – which quips that there is no external world – seems incorrigible.  It seems as though no matter how convincing ones arguments are, the skeptic will always be prone to say, “That’s a good argument, but it’s possible that you’re wrong.”  And on the basis of that retort alone, they’ll continue on spouting their skepticism.  What to do with people like this (if any such people exist)?  Simply leave them alone.  They aren’t going to change their minds.  Don’t waste your time.  We’ll talk about replies to this in the next section.

Easy enough.  Don’t argue with skeptics about the external world.  But what about people who seem to be just as “stuck” in their beliefs as the global skeptic?  Here’s a handy evidentialist (more on Evidentialism in the next article) way of knowing when someone might actually change their beliefs:

1) You’ve built a positive case for your position that is more plausible than your opponent’s

2) You’ve sufficiently rebutted or refuted their position

3) You’ve undercut their position by showing them possible defeaters to it

4) You’ve shown them that your position is the only alternative to theirs.  Or, you’ve shown them that among all of the possible alternatives, your position is the most plausible

If after all of that, your interlocutor is unwilling to give up his position and move to yours, he might be bouncing around in the labyrinth between cogency and psychological bias[iii], or perhaps he has one last legitimate concern.  It’s parallel to a response one might make to a skeptical argument that tries to show there is no external world.  Let’s find out what it is.

1.1 Moorean Facts

Here are some commonsense examples of Moorean facts:

1) Things move

2) Induction is rational

3) The past actually happened

Here are more controversial candidates:

1) Moral perception corresponds to reality

2) God (or something like God) exists

3) I am not the same thing as my body (that is, I am not a wholly material, physical object)

Princeton philosopher Thomas Kelly, following GE Moore, wrote a paper titled “Moorean Facts and Belief Revision, or Can the Skeptic Win?”[iv] In the paper he tries to wrestle through this question of skepticism and belief revision.  Suppose, as stated in the intro, you encounter a skeptic who claims that there isn’t really an external world, and so you don’t really have any hands.  They are merely projections of your mind.  An initial Moorean response to the skeptic includes naming something wrong with the argument without knowing what it is.  By assuming that there is a hidden flaw in the argument one can deflate it.  Or the Moorean can sift through the arguments against his position that he’s encountered thus far, and conclude that they were all failures.  Then a prediction can be made that skeptical arguments will continue to fail in the future.  An even stronger policy is to claim that any argument that has the denial of a Moorean fact as its conclusion should be rejected!  Nice.

The thing to note is that, in the end, we believers in the external world can reject the skeptic’s argument even if we can’t put our finger on what’s wrong with it.  Is this dogmatic and narrow-minded?  We’ll find out in the next section which is in the second post of this essay.  I’ve called it “Belief Revision: Part 2.”  And yes, I came up with the title all by myself.

Take me to part 2!

[i] (My paraphrase).  This almost legendary argument comes from his “A Defense of Common Sense” which can be found here:

[ii] Global skeptics are those that are skeptical about everything.  It’s unlikely that people like this exist, and it’s used more as a heuristic (learning) device in philosophy to test the plausibility of theories and arguments (kind of like a “good” hacker poking holes in the security systems of computers).


[iv] The paper can be found here:


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