THE present volume of the Selected works of Lenin covers theperiod of the First Russian Revolution of 1905-07,which,accord-ing to the profound remark of Lenin，represented the “dressrehearsal” of the Revolution of 1917.

During this period, in which the Russian working classemerged on the broad political arena of mass action，a numberof very important problems of principle and of tactics arose forsolution. It became obvious that the divergences within the Partyon questions of organisation，which became revealed at the Sec-ond Party Congress held in London in 1903，were actually widerand deeper than hadappeared at the time. Behind differentviewpointson questions of Party organisation there loomedentirely opposite conceptions of the role and tasks of the prole-tariat in the revolution,opposite conceptions of the attitudetoward other classes and parties which ostensibly were marchingtogether against the autocracy，and there were profound differ-ences on practically every question concerning principles andtactics. In 'short,it was found that the old Economism of thcnineties of the last century was not dead and buried,but thatit had survived in the theories and practice of the Mensheviks,and that the latter were nothing but the Russian variety ofrevisionism and opportunism which at that time were alreadyseriously sapping the strength of the Socialist Parties in WesternEurope.Moreover，in addition to the Mensheviks，who by theirtactics and teachings tried to restrict and debase the labourmovement and subject it to the bourgeoisie，there were others(Trotsky and Parvus,the Socialist-Revolutionaries) whose high-sounding“Left”phrases merely served as a screen for the samepetty-bourgeois influence over the proletariat that the Mensheviksrepresented and who tried to divert the movement from its propercourse.Trotsky's"absurdly‘Left’theory of permanent revolution," as Lenin called it,eventually landed him in the vanguardof the counter-revolutionary bourgeoisie; and the Socialist-Rev-olrtionaries proved themselves to be what Lenin had _calledthem，viz.,petty-bourgeois democrats masquerading under so-cialist phrases,by the whole of their subsequent conduct whichended in open counter-revolutionaryaction after the OctoberRevolution.