Here is one hand

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Here is one hand is a famous argument by G. E. Moore aimed at defeating skeptical doubts about the external world and defending common sense. Skeptics propose scenarios like evil demons or brains in vats that make it seem we cannot know that any ordinary things exist. Moore doesn’t try to defeat those skeptical hypotheses by arguing about their logic directly. Instead he uses a so‑called Moorean shift: he accepts the skeptic’s first premise (that a skeptical possibility could be true) but denies its conclusion, then uses that denial as the second step of his own argument. The dramatic example from his 1939 essay Proof of an External World is simple: he holds up one hand and says, “here is one hand,” then holds up the other and says, “and here is another.” The claim he wants us to know is not just that he sees hands, but that there are two external, material hands. If the external world exists, the skeptical scenario is false.

Moore also lays out three requirements for a good proof: the premises must be different from the conclusion, the premises must be known, and the conclusion must follow from the premises. He argues that his proof meets these criteria and shows that common-sense knowledge (for example, that there are hands) is more reasonable than the distant, skeptical alternatives.

In his 1925 Defence of Common Sense, Moore argues against skepticism about the external world by saying that skeptics cannot provide reasons stronger than the reasons we have for believing everyday claims we actually know, such as “I have hands.” He claims it is more reasonable to believe we have hands when we see them than to accept the skeptical alternative described as a “strange argument in a university classroom.”

Many later philosophers have challenged Moore. Some say his method is unconvincing or circular. A key critique is that Moore’s argument seems to rely on a premise (that we know we have hands) in order to justify knowledge of the external world, and that the justification doesn’t necessarily transfer to the broader conclusion. This line of critique is what Crispin Wright called the problem of transmissiveness: Moore’s evidence for knowing there is a hand would require independent justification for believing the world is the kind of thing that makes that hand exist.

James Pryor responds by distinguishing two ideas about perception. Some thinkers are “conservatives” about perception, who think you need independent justification to rule out error (like the possibility you’re dreaming) before you can have knowledge from perception. Pryor argues for a more permissive view, which he calls perceptual dogmatism: if you have an experience as if something is the case, you have immediate justification for believing it, without needing extra independent support. On this view, Moore’s argument could be seen as transmissive and could justify beliefs about the external world through perception. But Pryor says the debate is mainly about whether the proof will convince someone who already doubts the conclusion.

Ludwig Wittgenstein offered a subtle challenge from his work On Certainty. He suggested that saying “I know” has its own language‑game, and knowing one thing does not automatically entail knowing another. This means Moore’s claim to knowledge might be more complex than it first appears.

Moretti later offered another take: since Moore has the experience that there is a hand, he would directly obtain justification for both “there is a hand” and “there is something material,” making Moore’s proof seem odd or even useless for proving the external world to someone who doesn’t already share Moore’s intuition.

In short, Moore’s “Here is one hand” argument stays a touchstone in debates about how we justify common-sense beliefs against radical skeptical challenges. It sparked a long-running discussion about what counts as knowledge, how justification works, and whether perceptual experience alone can ground belief in the external world.