Marxian economics is thus a study of abstract working society showing the variations which this undergoes in the different social economic organisations. This investigation Marx carried out only in reference to one of these organisations, _i.e._ the capitalist; contenting himself with mere hints in regard to the slave and serf organisations, primitive communism, the domestic system and to savage conditions.[29] In this sense he and Engels declared that economics (the economics studied by them), was an historical science.[30] But here, too, their definition has been less happy than the investigation itself; we know that Marx's researches are not historical, but hypothetical and abstract, _i.e._ theoretical.[31] They might better be called researches into _sociological economics_, if the word _sociological_ were not one which is employed most variously and arbitrarily. If Marx's investigation is thus limited, if the law of value postulated by him is the special law of an abstract working society, which only partially takes effect in economic society as given in history, and in other hypothetical or possible economic societies, the following results seem to follow evidently and readily: (1) That Marxian economics _is not general economic science_; (2) that labour-value _is not a general concept of value_. Alongside, then, of the Marxian investigation, there can, or rather must, exist and flourish a general economic science, which may determine a concept of value, deducing it from quite different and more comprehensive principles than the special ones of Marx. And, if the pure economists, confined to their own special province, have been wrong to show an ungenerous intellectual dislike for Marx's investigations, his followers, in their turn, have been wrong to regard ungratefully a branch of research which was alien to them, calling it now useless, and now frankly absurd. Such is, in effect, my opinion, and I freely acknowledge that I have never been able to discover other antithesis or enmity between these two branches of research except the purely accidental one of the mutual antipathy to and mental ignorance of each other, of two groups of students. Some have resorted to a political explanation; but, with no wish to deny that political prepossessions are often the causes of theoretical errors, I do not consider an explanation as adequate and appropriate, which resolves itself into accusing a large number of students of allowing themselves blindly and foolishly to be overcome by passions alien to science; or, what is worse, of knowingly falsifying their thought and constructing a whole economic system from motives of practical opportunism.