In the spirit of Frege's gripping opener in “Ueber Sinnund Bedeutung”, one can equally well say that the concept of existence challenges reflection; for how can one deny that Pegasus exists without presuming existence? After all, such claims can be informative, for they could be false. Consequently, one might argue, they must say something about something. Thus, they succeed in being, in a back-handed, paradoxical way, existence statements of a sort. This problem is very old; it is Plato's problem of non-being. Frege's solution to the problem is also well known.
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