Here is a hand
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Here is a hand (or "aw come on") is the name of a philosophical argument created by George Edward Moore against Philosophical skepticism and in support of common sense. The argument has become famous among philosophers.
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[edit] Introduction
Skeptical hypotheses, such as "you may be dreaming" or " the world is 5 minutes old", create a situation where it is not possible to know that anything in the world exists. They do so in the following form:
The Skeptical Argument
Where S is a subject, sp is a skeptical possibility, such as the brain in a vat hypothesis, and q is a knowledge claim about the world:
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- S doesn't know that not-sp
- If S doesn't know that not-sp, then S doesn't know that q
- Therefore, S doesn't know that q
Moore's response
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- S knows that q
- if S doesn't know that not-sp, then S doesn't know that q
- Therefore, S knows that not-sp
Moore does not attack the skeptical premise, instead, he reverses the argument from being in the form of Modus Ponens to Modus Tollens (see below).
[edit] Explanation
Moore famously put the point into dramatic relief with his 1939 essay "Proof of an External World", in which he gave a common sense argument against skepticism by raising his right hand and saying "here is a hand," and then raising his left and saying "and here is another". Here, Moore is taking his knowledge claim (q) to be that he has two hands, and without rejecting the sceptic's premise, proves the we can know the skeptical possibility (sp) to be not true.
Moore's argument is not simply a flippant response to the skeptic. Moore gives in "Proof of an External World", three requirements for a good proof. (1) the premises must be different from the conclusion, (2) the premises must be demonstrated, and (3) the conclusion must follow from the premises. He claims that his proof of an external world meets those three criteria.
In his 1925 essay "A Defence of Common Sense" he argued against idealism and skepticism toward the external world on the grounds that they could not give reasons to accept their metaphysical premises that were more plausible than the reasons we have to accept the common sense claims about our knowledge of the world that skeptics and idealists must deny. In other words, he is more willing to believe that he has a hand than believe the premises of a strange argument in a University classroom. "I do not think it is rational to be as certain of any one of these ... propositions"[1].
Not surprisingly, not everyone inclined to skeptical doubts found Moore's method of argument entirely convincing; Moore, however, defends his argument on the (surprisingly simple) grounds that skeptical arguments seem invariably to require an appeal to "philosophical intuitions" that we have considerably less reason to accept than we have for the common sense claims that they supposedly refute.
[edit] Logic
The skeptical argument takes the form of Modus Ponens: If A then B. A. Therefore B.
Moore's argument flips the Modus Ponens structure into a Modus Tollens: If A then B. Not B. Therefore not A.
"one man's modus ponens is another man's modus tollens" (Dretske 1995 [2]).
[edit] Effect
Appeals of this type are subsequently often called "Moorean facts". "A Moorean fact [is] one of those things that we know better than we know the premises of any philosophical argument to the contrary"[1].
The "here is one hand" idea, in addition to fueling Moore's own work, also deeply influenced Wittgenstein, whose last writings were devoted to a new approach to Moore's argument. These remarks were published posthumously as On Certainty.
[edit] References
- ^ a b Keith DeRose, Responding to Skepticism
- ^ Steve Lehar, Philosophical jargonology
[edit] External links
- Kelly, Thomas. Moorean Facts and Belief Revision, or Can the Skeptic Win?. Princeton University. Forthcoming in John Hawthorne (ed.), Philosophical Perspectives, vol.19: Epistemology. [1]
| Skeptical hypotheses |
|---|
| Evil Daemon | Brain in a vat | Dream argument | 5 minute earth |
| Responses |
| Here is a hand | Semantic externalism | Process reliabilism | Closure | Contextualism | Relativism |
