The "communists"--that is, the political party for which the "Communistic Manifesto" serves as a confession of faith--are only a part of the warring proletariat; they form that part which is conscious of the process of development. This party "distinguishes itself from the other proletarian elements only in that on the one side it emphasises and enforces in the different national campaigns of the proletariat the interests of the proletariat as a whole, and on the other hand in that in the different stages of development through which the struggle between the proletariat and the bourgeoisie passes, invariably it represents the interests of the general proletarian movement." "The theories of the communists rest in no way upon ideas or principles which have been discovered by this or that reformer. They are only general expressions of the actual conditions in an existing struggle of classes, an agitation which is happening historically before our very eyes." The thoughts here expressed, as I have already indicated in several places in this review, have been later to some extent more precisely worded, have been to some decree enlarged and developed, have been in part modified; but the ground-lines of Marx's theory of the social movement are already revealed in them all. In what now lies their historic importance? How shall we explain their tremendous power of conquest? Whence comes their continuance already through a half-century?--and all this, in spite of the fact that, as I believe, this theory errs in essential points, and that it can scarcely indeed sustain itself as a whole!