It might be supposed that one might use "a kind of ostensive definition" for S, by focusing on the sensation and on the symbol. Early in The Investigations, Wittgenstein attacks the usefulness of ostensive definition.[7] He considers the example of someone pointing to two nuts while saying "This is called two". How does it come about that the listener associates this with the number of items, rather than the type of nut, their colour, or even a compass direction? One conclusion of this is that to participate in an ostensive definition presupposes an understanding of the process and context involved, of the form of life.[8] Another is that "an ostensive definition can be variously interpreted in every case". — Wikipedia
That doesn't say ostensive definitions are impossible. If you go to the PI, and read §28 and onwards, you might get a different view. — Banno
Turns out the quote you cite was inserted (begun) by yours truly, back in 2006. — Banno
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