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Ludwig Wittgenstein’s On Certainty, and how G.E. Moore Fails to Respond to the Skeptics (Part 3)

March 20th, 2008

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He is not presenting a skeptical challenge to knowledge of mathematics.

At the crux of his argument, Wittgenstein rejects the Cartesian-style premise that all propositions, even foundational ones, should be doubted along with any beliefs that they justify, unless they can be proven empirically. The skeptics’ doubt of these propositions does not merely test the truth, falsehood, or likelihood of those propositions, but ultimately necessitates questioning the methods by which testable empirical propositions are tested (317, 318). If all knowledge is based on testable empirical propositions that are justified by methods that are themselves subject to the skeptics’ pervasive doubt, then one must always acknowledge skeptical possibilities (i. e. the skeptics’ position is meaningful).

To counter this, Wittgenstein explains that claims like “here is a hand” or “the world has existed for longer than five minutes” merely appear to be statements about the external world that are true or false. However, these propositions lie beyond knowledge or doubt, because they serve as the framework by which we can speak about objects in the world. He uses two metaphors: first, that these kinds of propositions are like a “river-bed” that allow the “river of language” to flow freely (97, 99); and second, that the propositions are like hinges on a door, which must be fixed in order for the door to function in any significant way (341, 343). These kinds of propositions ostensively defined; they are not making an empirical claim about the external world, but merely show an example and hence demonstrate how the statement is to be used. The possibility of language is not made by actual facts in the world (which the skeptic can always undermine), but by simply never calling into question those facts (creating the “river-bed”). [4] Thus, Wittgenstein does superficially agree with the skeptic that such foundational propositions lie beyond empirical verification, but questions the sensibility and usefulness of such an assertion.

Objection to Moore’s Objections

G. E. Moore attempted his own refutation of skepticism, toward which On Certainty was inspired and directed to a large degree. Moore wrote several articles in challenging skepticism, including A Defense of Common Sense, Four Forms of Skepticism, and Proof of an External World. His general objection can be summarized by taking the skeptics’ modus ponens and using the same conditional to form a modus tollens argument. Using the same example as earlier, Moore would argue,

  1. If I can not distinguish between dreaming and being awake, then I can not be sure I have a body.
  2. I am sure I have a body.
  3. Therefore, I can distinguish between dreaming and being awake.

Though Moore is correct in challenging that doubting such basic claims is unreasonable, Wittgenstein suggests that Moore still fails to answer the skeptic because Moore’s claim that he knows he has a hand is subject to the question of how he knows- bringing him back to the beginning of the argument with the skeptics.

Furthermore, Wittgenstein accepts Moore’s propositions, but not his subjective assurance that they are true. The meaning of the phrase “I know that…” is initially explained in demonstrating the insufficiency of Moore’s arguments against skepticism. Firstly, “P” can not be properly inferred from someone’s statement, “I know P. ” While “P” can be inferred from “he knows P,” this requires justification (13, 14). The assurance “I know” is insufficient to demonstrate that no mistake is possible (15). Besides the contextual exceptions of the usage of “I know” (“I can not be wrong,” “I thought I knew,” etc. the phrase is insignificant; if one actually knows that something is the case, then it is the case.

He then proceeds to argue, “Moore’s mistake lies in this – countering the assertion that one cannot know that, by saying ‘I do know it’” (521). Since skepticism is nonsense, as Wittgenstein establishes, it need not and can not be refuted by a counter-example. Moore, actually, commits the same error as the skeptic by treating logic (which is founded on those basic propositions) as empirical statements requiring proof.

Wittgenstein makes a general statement about Moore’s argument, which also happens to be a repetition of one of the most important themes of On Certainty:

When Moore says he knows such and such, he is really enumerating a lot of empirical propositions which we affirm without special testing; propositions, that is, which have a peculiar logical role in the system of our empirical propositions (136).

Moore did not recognize this, instead attempting to answer the skeptic on epistemological grounds.

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