To this economic hierarchy corresponds, according to various modes, in different countries, in different times, in different places, what I may call almost a hierarchy of souls, of intellects, of minds. That is to say, that culture, which, for the idealists, constitutes the sum of progress, has been and is by the necessities of the case very unequally distributed. The greater portion of mankind, by the quality of their occupations, are composed of individuals who are disintegrated, broken into fragments and rendered incapable of a complete and normal development. To the economics of classes and to the hierarchy of social positions corresponds the psychology of classes. The relativity of progress is then for us the inevitable consequence of class distinctions. These distinctions constitute the obstacles which explain the possibility of relative retrogression, up to the point of degeneracy and of the dissolution of an entire society. The machines, which mark the triumph of science, become, by reason of the antithetic conditions of the social plexus, instruments which impoverish millions and millions of artisans and free peasants. The progress of technique, which fills the towns with merchandise, makes more miserable and abject the condition of the peasants, and in the cities themselves it further humbles the condition of the humble. All the progress of science has served thus far to differentiate a class of scientists and to keep ever further from culture the masses who, attached to their ceaseless daily toil, are thus feeding the whole of society. Progress has been and is, up to the present time, partial and one-sided. The minorities which share in it call this human progress; and the proud evolutionists call this human nature which is developing. All this partial progress, which has thus far developed upon the oppression of man by man, has its foundation in the conditions of opposition, by which economic distinctions have engendered all the social distinctions; from the relative liberty of the few is born the servitude of the greater number, and law has been the protector of injustice. Progress, thus seen and clearly appreciated, appears to us as the moral and intellectual epitome of all human miseries and of all material inequalities. To discover this inevitable relativity it was necessary that communism, born at first as an instinctive movement in the soul of the oppressed, should become a science and a political party. It was then necessary that our doctrine should give the measure of value for all past history, by discovering in every form of social organization, antithetical in its origin and organization, as they have all been up to this time, the innate incapacity for producing the conditions of a universal and uniform human progress, that is to say, by discovering the fetters which turn each benefit into an injury. VI. There is one question which we cannot evade: What has given birth to the belief in _historic factors_?