Rule following

Wittgenstein on Rules and Private Language is a 1982 book by philosopher of language Saul Kripke, in which Kripke contends that the central argument of Ludwig Wittgenstein's Philosophical Investigations centers on a devastating rule-following paradox that undermines the possibility of our ever following rules in our use of language. Kripke writes that this paradox is "the most radical and original skeptical problem that philosophy has seen to date" (p. 60). He argues that Wittgenstein does not reject the argument that leads to the rule-following paradox, but accepts it and offers a 'skeptical solution' to alleviate the paradox's destructive effects.

While most commentators accept that the Philosophical Investigations contains the rule-following paradox as Kripke presents it, few have concurred in attributing Kripke's skeptical solution to Wittgenstein. Kripke expresses doubts in Wittgenstein on Rules and Private Language as to whether Wittgenstein would endorse his interpretation of the Philosophical Investigations. He says that the work should not be read as an attempt to give an accurate statement of Wittgenstein's views, but rather as an account of Wittgenstein's argument "as it struck Kripke, as it presented a problem for him" (p. 5). The portmanteau "Kripkenstein" has been coined as a nickname for a fictional person who holds the views expressed by Kripke's reading of the Philosophical Investigations; in this way, it is convenient to speak of Kripke's own views, Wittgenstein's views (as generally understood), and Kripkenstein's views. Wittgenstein scholar David G. Stern considers the book to be the most influential and widely discussed work on Wittgenstein since the 1980s.

In PI 201a Wittgenstein explicitly states the rule-following paradox: "This was our paradox: no course of action could be determined by a rule, because any course of action can be made out to accord with the rule". Kripke gives a mathematical example to illustrate the reasoning that leads to this conclusion. Suppose that you have never added numbers greater than 50 before. Further, suppose that you are asked to perform the computation '68 + 57'. Our natural inclination is that you will apply the addition function as you have before, and calculate that the correct answer is '125'. But now imagine that a bizarre skeptic comes along and argues:

After all, the skeptic reasons, by hypothesis you have never added numbers greater than 50 before. It is perfectly consistent with your previous use of 'plus' that you actually meant it to mean the 'quus' function, defined as:

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