{"agent_id":"moore","agent_name":"G.E. Moore","slug":"proof-of-an-external-world","label":"Proof of an External World: does 'here is one hand' constitute a valid proof of the existence of material objects?","topic":"Proof of an External World","question":"Does 'here is one hand' constitute a valid proof of the existence of material objects?","position":"The proof has the form: Premise 1: Here is one hand. Premise 2: Here is another. Conclusion: Therefore, at least two material objects exist; therefore, an external world exists. The proof is rigorous in the senses that matter for proof: the premises are different from the conclusion; the premises are more certain than the conclusion of any skeptical argument; the inference is valid. The objection \"but how do you KNOW you have hands?\" misunderstands what the proof claims. The proof does not claim to address that question; it claims that the question of whether material objects exist is settled by the holding-up of the hands plus the inference. If I know I have hands (and I do — this is one of the truisms of the 1925 Defence), then I know material objects exist. If someone denies that I know I have hands, they are denying something more certain than any premise that would lead to the denial. The proof is therefore a proof in the strict sense; what it does not do is provide a non-question-begging response to the philosophical skeptic about external-world knowledge in general — but that is a separate question. The anti-skeptical work the proof actually does is structural: it shows that the existence of an external world can be demonstrated within the framework of common-sense certainty, without needing to engage the skeptic's general challenge on its own terms.","paragraphs":[[{"t":"The proof has the form: Premise 1: Here is one hand.","n":[]},{"t":"Premise 2: Here is another.","n":[]},{"t":"Conclusion: Therefore, at least two material objects exist; therefore, an external world exists.","n":[]},{"t":"The proof is rigorous in the senses that matter for proof: the premises are different from the conclusion; the premises are more certain than the conclusion of any skeptical argument; the inference is valid.","n":[]}],[{"t":"The objection \"but how do you KNOW you have hands?\" misunderstands what the proof claims.","n":[]},{"t":"The proof does not claim to address that question; it claims that the question of whether material objects exist is settled by the holding-up of the hands plus the inference.","n":[1,2]},{"t":"If I know I have hands (and I do — this is one of the truisms of the 1925 Defence), then I know material objects exist.","n":[]}],[{"t":"If someone denies that I know I have hands, they are denying something more certain than any premise that would lead to the denial.","n":[]},{"t":"The proof is therefore a proof in the strict sense; what it does not do is provide a non-question-begging response to the philosophical skeptic about external-world knowledge in general — but that is a separate question.","n":[3]}],[{"t":"The anti-skeptical work the proof actually does is structural: it shows that the existence of an external world can be demonstrated within the framework of common-sense certainty, without needing to engage the skeptic's general challenge on its own terms.","n":[4,5]}]],"texts":"'Proof of an External World' (Proceedings of the British Academy 1939, in Philosophical Papers 1959 and Selected Writings); 'A Defence of Common Sense' (1925) for the related anti-skeptical strategy; 'Certainty' (in Philosophical Papers); 'Four Forms of Scepticism' (in Philosophical Papers). Reception: Ludwig Wittgenstein On Certainty (1969); Barry Stroud The Significance of Philosophical Skepticism (1984), the major contemporary objection; James Pryor 'The Skeptic and the Dogmatist' (Nous 2000) on dogmatist responses; Crispin Wright 'Facts and Certainty' (1985) and his work on Mooreanism; Duncan Pritchard Epistemic Angst (Princeton 2015) on contemporary anti-skepticism; Annalisa Coliva Moore and Wittgenstein: Scepticism, Certainty, and Common Sense (Palgrave 2010); Thomas Baldwin G.E. Moore (1990) Chapter IX.","works":["'Proof of an External World' (Proceedings of the British Academy 1939, in Philosophical Papers 1959 and Selected Writings)","'A Defence of Common Sense' (1925) for the related anti-skeptical strategy","'Certainty' (in Philosophical Papers)","'Four Forms of Scepticism' (in Philosophical Papers)"],"reception":"Ludwig Wittgenstein On Certainty (1969); Barry Stroud The Significance of Philosophical Skepticism (1984), the major contemporary objection; James Pryor 'The Skeptic and the Dogmatist' (Nous 2000) on dogmatist responses; Crispin Wright 'Facts and Certainty' (1985) and his work on Mooreanism; Duncan Pritchard Epistemic Angst (Princeton 2015) on contemporary anti-skepticism; Annalisa Coliva Moore and Wittgenstein: Scepticism, Certainty, and Common Sense (Palgrave 2010); Thomas Baldwin G.E. Moore (1990) Chapter IX.","status":"The 1939 Proof is one of the most-discussed texts in twentieth-century epistemology. Stroud's The Significance of Philosophical Skepticism (1984) is the major contemporary critique. The contemporary debate divides between dogmatists (Pryor) who hold the proof works because perceptual experience gives immediate justification for the premises, conservativists (Wright) who hold the proof requires antecedent entitlement to the relevant background commitments, and skeptics who hold the proof fails to engage the skeptic's actual concern. Coliva's Moore and Wittgenstein (2010) is the major contemporary systematic study. The position remains contested.","era":"1873-1958","discipline":"Philosophy","refs":[{"n":1,"work":"Philosophical Papers","page":"pp. 145–146","canonical":"","quote":"I can prove now, for instance, that two human hands exist. How? By holding up my two hands, and saying, as I make a certain gesture with the right hand, 'Here is one hand', and adding, as I make a certain gesture with the left, 'and here is another'.","label":"Philosophical Papers, pp. 145–146"},{"n":2,"work":"EXTERNAL AND INTERNAL RELATIONS","page":"pp. 177–178","canonical":"","quote":"I can prove now, for instance, that two human hands exist. How? By holding up my two hands, and saying, as I make a certain gesture with the right hand, 'Here is one hand', and adding, as I make a certain gesture with the left, 'and here is another'.","label":"EXTERNAL AND INTERNAL RELATIONS, pp. 177–178"},{"n":3,"work":"Philosophical Papers","page":"p. 148","canonical":"","quote":"But now I am perfectly well aware that, in spite of all that I have said, many philosophers will still feel that I have not given any satisfactory proof of the point in question. And I want briefly, in conclusion, to say something as to why this dissatisfaction with my proofs should be felt. One reason why, is, I think, this.","label":"Philosophical Papers, p. 148"},{"n":4,"work":"Philosophical Papers","page":"pp. 146–147","canonical":"","quote":"And if such a thing as that could ever be certain, then assuredly it was certain just now that there was one hand in one of the two places Jindicated and another in the other.","label":"Philosophical Papers, pp. 146–147"},{"n":5,"work":"EXTERNAL AND INTERNAL RELATIONS","page":"p. 179","canonical":"","quote":"And I want to emphasise that, when Kant says it is a scandal not to be able to give a proof of the existence of external objects, a proof of their existence in the past would certainly help to remove the scandal of which he is speaking. He says that, if it occurs to anyone to question their existence, we ought to be able to confront him with a satisfactory proof.","label":"EXTERNAL AND INTERNAL RELATIONS, p. 179"}],"answer":null,"siblings":[{"slug":"the-refutation-of-idealism","label":"The Refutation of Idealism: does the idealist formula 'esse is percipi' confuse the act of perception with its object?"},{"slug":"the-naturalistic-fallacy","label":"The Naturalistic Fallacy: is goodness a simple, indefinable, non-natural property, with any naturalist reduction committing a fallacy?"},{"slug":"ideal-utilitarianism-the-principle-of-organic-unities","label":"Ideal Utilitarianism + the Principle of Organic Unities: are friendship and aesthetic experience the highest intrinsic goods?"},{"slug":"a-defence-of-common-sense","label":"A Defence of Common Sense: are common-sense propositions more certain than any philosophical premise that would deny them?"},{"slug":"sense-data-theory-the-paradox-of-analysis","label":"Sense-data theory + the paradox of analysis: are sense-data the immediate objects of perception, and how can a correct conceptual analysis be informative?"}]}