Abstract
"One of Frege's main semantic principles, is however, missing in Dummett's book, [Frege: philosophy of language] and it is has been ignored by most Frege scholars. That principle is the thesis concerning the ambiguity of the word 'is'. Angelelli come close to attending to it when he makes some remarks on identity and predication, and Matthias Schirn puts special emphasis on the role of the thesis in Frege's work. However, the great majority of Frege scholars have neglected the ambiguity doctrine, even when they have commented on each of the allegedly different meanings of 'is' separately. This is strange in view of the fact that it was Frege and Russell who proposed the thesis and established it as one of the basic ingredients of modern logic. They have in fact been followed by most philosophers. For instance, in the Tractatus Ludwig Wittgenstein emphasizes the ambiguity of the verb 'to be' and stresses the..