  The Stranger made a serious mistake about negation in the puzzles about not-being earlier in the dialogue (highlighted at Sophist 240b, 240d), in supposing that the negation in “not-being” indicates the opposite (enantion) of being. The opposite of being is nothing, and Parmenides is right that we cannot speak or think about nothing: if we speak or think at all, we speak or think about something. But Parmenides mistakenly thought that all talk about not-being is attempted talk about nothing.