This book is based on addresses and lectures which the author has delivered at different times since the 23rd Congress of the C.P.S.U. to various audiences, such as a general meeting of scientists at the U.S.S.R. Academy of Sciences, conferences of department heads and social science instructors of higher educational institutions, seminars of ideological workers in Moscow, Leningrad, Kiev, Tbilisi, Riga, Yaroslavl and other cities. Although the various sections stand more or less by themselves, the book as a whole is orientated towards a single aim—that of defending the basic ideas of Marxism-Leninism against the attacks of the ideologues of anti-communism and revisionism from both the Right and the “Left”. Needless to say, in preparing the manuscript for the press a good deal of extra work had to be done and new documentary sources drawn upon.