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“The apparent surface form of an expression, in comparison with the underlying logical structure. In any language some expressions may resemble others in appearance, yet differ fundamentally in their kind of meaning. Such expressions may then be said to be similar in grammatical, but different in logical form.
“In Through the Looking Glass Alice said she saw nobody on the road, and the King envied her her eyes: ‘It’s as much as I can do to see real people, by this light!’ Lewis Carroll was thus representing him as being misled by the similarity in grammatical form between ‘nobody’ and ‘somebody’ into construing both words as having the same logical form, that is, as both referring to a person.”
— A Dictionary of Philosophy (2nd ed.), Antony Flew, ed., 135.