I) Macedonian is a mixed language either of partly Illyrian origin -- such was the position of Müller himself, G. Kazaroff, M. Rostovtzeff, M. Budimir, H. Baric; or of partly Thracian origin, as it was maintained by D. Tzanoff.
II) Macedonian is a separate Indo-European language. This was the opinion of V. Pisani, I. Russu, G. Mihailov, P. Chantraine, I. Pudic, C. D. Buck, E. Schwyzer, V. Georgiev, W. W. Tarn and of O. Masson in his youth.
III) But according to most scholars Macedonian was a Greek dialect. This view has been expanded by F. G. Sturz, A. Fick, G. Hatzidakis, O. Hoffmann, F. Solmsen, V. Lesny, Andriotis, F. Geyer, N. G. L. Hammond, N. Kalleris, A. Toynbee, Ch. Edson and O. Masson in his mature years.
IV) Finally, a small number of scholars thought that the evidence available was not sufficient to form an opinion. Such was the view of A. Meillet and A. Momigliano.
Whatever the scientific merits of the above scholars, it was the nature of the evidence itself and, above all, its scarcity, which allowed the propounding of opinions so diverse and incompatible between themselves.