No finite set of examples can ever fix what a rule actually means

Show someone the sequence 2, 4, 6, 8 and they'll say the rule is "add two" — but the same data fits infinitely many other rules, like "add two until 1000, then add four." Wittgenstein argued nothing in your past use of a word logically forces one interpretation over any of these bizarre alternatives. Kripke later sharpened this into a full skeptical paradox about whether words can mean anything at all.

— Ludwig Wittgenstein, Philosophical Investigations — §201; sharpened by Saul Kripke in "Wittgenstein on Rules and Private Language," 1982
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