I wish to express, first of all, my profound gratitude to Professor J. M. Bochenski, without whose assistance the present work would have not been possible. To be concise, I would like to state that his contribution to this book may be viewed at three levels: (1) that of the general spirit, (2) that of the specific ideas, theses or approaches which are expressed in its pages, (3) that of this work qua doctoral dissertation. The general spirit which has guided my research coincides with that underlying Professor :Oochenski’s own works, in particular his Formale Logik (Munchen 1956). Moreover, the particular occasion which suggested my investigation was a statement included in that book according to which the literature in the field still lacked a detailed work on Frege (p. 317). I wish, likewise, to express my gratitude to other professors of the University of Fribourg for their generous help. I mention especially Professors P. Wyser, M. D. Philippe, N. Luyten, and V. Kuiper. I have also benefited from Professor E. Specker’s lectures at the Eidge- nossische Technische Hochschule (ZUrich) and from Professor Olof Gigon’s lectures at the University of Bern. From an earlier period I wish to express my gratitude to the professors of the philosophy department of the Universidad Nacional de Buenos Aires, especially the late Professor Francisco Romero. The Swiss National Library (Bern) has greatly facilitated access to bibliographical sources, and the library of the University of Munster (Westphalien) has kindly provided microfilms of Frege’s Nachlap.