If "x" is a name, "x=x" is not the same proposition as "the author of Waverly is the author of Waverly," no matter what name "x" may be. ... When we substitute a [definite] description for a name, propositional functions which are "always true" may become false, if the description describes nothing [e.g., 'the present King of France'].
Google-1
Google-2
Published before 1923