This was not the only change which the League underwent. Its members began to understand that their real duty under the present circumstances was not conspiracy or the stirring up of revolutionary outbreaks, but propaganda. The basis of the League had been a sentimental communism, based on their motto that ‘all men are brothers.’ From Marx they learned that the emancipation of the proletariat must be guided by scientific insight into the conditions of its own existence and its own history; that their communism must indeed be a revolutionary one, but it must be a revolution in harmony with the inevitable tendencies of social evolution. The cardinal point in the theory worked out by Marx and now impressed upon the League, was the doctrine that the economic conditions control the entire social structure, therefore the main thing in a social revolution is a change in economic conditions. The group of exiles put themselves into communication with Marx, and a Congress was held in London in 1847, with the result that the association was reorganised under the name of the Communist League. The aim of the League is very comprehensively stated in the first article of its constitution: ‘The aim of the League is the overthrow of the _bourgeoisie_, the rule of the proletariat, the abolition of the old society resting on class antagonisms, and the founding of a new society without classes and without private property.’ Marx and Engels were commissioned by the League to set forth its principles in a manifesto, which, as the manifesto of the communistic party, was published shortly before the Revolution of February 1848. We shall best illustrate the spirit and aim of the treatise by quoting Fr. Engels’ Preface to the edition of 1883:— ‘The Preface to the present edition I must, alas! sign alone. Marx, the man to whom the entire working class of Europe and America owes more than any other—Marx rests in the cemetery at Highgate, and the grass already begins to grow over his grave. Since his death nothing further can be said of a revisal or completion of the manifesto. It is therefore the more necessary expressly to make the following statement.