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On G.E. Moore’s "Proof of the External World" (1939) and "Certainty" (1941), featuring Mark, Wes, Dylan, and Seth.
Similar to the essay we covered in our last episode, Moore is defending common sense realism against idealists who claim that the external world is not mind-independent but is instead made up of ideas, and also skeptics who claim that we can't know (or know with certainty) anything about the external world. Instead of considering general claims that everyone presumably knows like "We as people have bodies and experiences and exist in space" and "The earth has existed for many years before we were born," Moore here argues based on "this is a hand" (while holding up his hand) to supposedly prove that external objects exist.
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There's some set-up in the "External World" essay before he makes this argument, because of course the skeptic and idealist would be fine with you claiming that you have a perception of a hand, just not with the argument that this thing, the hand, is an object with mind-independent reality, and that we can know that (in fact, it's totally obvious). He first distinguishes between things "presented in space," which could include, for instance, my pain (which is presented as being in my foot, for instance); from things "met with in space," which include exclude such private experiences but which imply that the thing would be there to be potentially met with even if no one is actually meeting with it (perceiving it or thinking about it or in any way mentally interacting with it). With this analysis, Moore thinks he's conceptually shown that things "met with in space," which include all physical objects (as well as shadows and other things), are thus external to our minds: They are objective and would exist even if perceiving creatures did not exist at all.
With that move, the philosophical work has been done. All he then has to show in his famous hand proof is that one thing met with in space exists (actually he points out both of his hands, so he's proved "things" instead of just a single "thing"), and that proves that the idealists are wrong.
But what about the skeptics? Moore uses the premise that these hands exist along with his conceptual analysis of what hands really are (physical objects, i.e. met with in space) to prove his general conclusion, but why would the skeptic accept that Moore has warrant to state the premise that his hands exist? As we'll consider in our upcoming episode on Wittgenstein's On Certainty, Wittgenstein was very struck my this: On the one hand, it's pretty inconceivable that you could think that you're looking at your own hand and be making a mistake about it. Wittgenstein can imagine some particular situations where that's the case (like you've taken drugs or are an amputee), but in ordinary situations, you can't make a mistake, and so it's actually weird to say you "know" that that's your hand, because knowledge implies some potential doubt and some method of proof, where the hand just seems too immediate to allow for either of these.
On the other hand (to continue this unfortunate verbal convention given that we're talking about the existence of hands), Moore is clearly just not taking the skeptic seriously that maybe all of our perceptions could be mistaken (because we're a brain in a vat, dreaming, in the Matrix, etc.). While Wittgenstein is then going to distinguish between the two different contexts ("language games") of ordinary interaction (where you can't be mistaken about the hand), and philosophical epistemology (where such doubts can at least be usefully entertained), Moore just says that investigation has to stop somewhere, and there are just some types of claims that we can know with certainty without being able to give reasons for why we know them. An argument uses premises to prove a conclusion. If we always demanded "well, sure, those premises lead to that conclusion, but you have to prove your premises!" then arguments would go on forever. You'd come up with a further argument to prove a premise, but then your premises in that argument would need to be similarly proved, ad infinitum. So we have a choice of just saying that we know absolutely nothing (and what would motivate this? Some claims about epistemology that would themselves be unproven and hence unknown!) or that there are some things that we just know without proof. We'll talk more about the status of these "Moorean sentences" in part two of this discussion.
Read the essays online: "Proof of an External World" and "Certainty."
Image by Solomon Grundy. Audio editing by Tyler Hislop.
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