You may say: Two can be defin[t|e]d ostensively only in thisch way: “This number is called ‘two’”[,|.] [f|F]or the word “number” shows here in what place in the our language – in the our grammar – we set ˇput assign to the word; but this means that the word “number” must be explained before that ostensive definition can be understood. – The word “number” in the definition does
indeed
certainly
indicate this place, the post to which we assign ˇto the word. And we can prevent misunderstandings in this way, by saying, “This colour is called so and so”, “This length is called so and so”, etc.. That is: misunderstandings are often avoided in this way. But can the word “colour”, then, or “length”, be understood [i|o]nly in this way? – Well, we'll ˇshall have to explain them. ˇThat is[|,] [E|e]xplain them by ˇmeans of other words, that is! And what about the last explanation in this chain? (Don't say: “There isn't any ‘last’ explanation”;. [t|T]h[at|is] is exactly as though you were to sa[y|id], “There isn't any last house in this street: you can always build ˇanother one further”.) .”)
      Whether the word “number” ˇis necessary in the ostensive definition of two is necessary depends on ˇupon whether he understands this word differently takes this word in a different sense from the way I wish him to the one I wish ˇmisunderstands my definition if I leave out the word. And th[at|is] will depend on the circumstances under which I give it the definition is given and on the person to whom I give it.
20
give it.
      And how he “understands” the explanation ˇwill appears in how the way he makes use of th[w|e] word explained.