Numbers are in a certain precise sense, formal. The relation of the symbol two to the meaning of a proposition in which it occurs is far more complicated than the relation of the symbol red to the meaning of a proposition in which it occurs. We may say, in a certain sense, that the symbol two means nothing, for, when it occurs in a true statement, there is no corresponding constituent in the meaning of the statement. We may continue, if we like, to say that numbers are eternal, immutable, and so on, but we must add that they are also logical fictions.p. 156.

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