[26] Hence also Marx in §4 of Chap. I.: _Der Fetischcharakter der Waare und sein Geheimniss_ (I. pp. 37-50) gave a brief outline of the other economic systems of mediæval society, and of the domestic system: 'Aller Mysticismus der Waarenwelt, all der Zauber und Spuk, welcher Arbeitsprodukte auf grundlage der Waarenproduktion umnebelt, verschwindet daher sofort, sobal wir zu anderen Producktions formen flüchten' (p. 42). The relation between value and labour appears more clearly in the less complex economic systems, because less opposed and obscured by other facts. [27] _Das Kapital_, Book III., sec. III., Chaps. XIII., XIV., XV., _Gesetz des tendentiellen Falls der Profitrate_ (vol. iii., Part I, pp. 191-249). [28] The task of Marx's followers ought to be to free his thought from the literary form which he adopts, to study again the questions which he propounds, and to work them out with new and more accurate statements, and with fresh historical illustrations. In this alone can scientific progress consist. The _expositions_ made hitherto of Marx's system, are merely _materials_; and some (like Aveling's) consist entirely in a series of little summaries, which follow the original chapter by chapter and prove even more obscure. For the law of the fall in the rate of profits, see below, chap. V. [29] 'To follow out completely this criticism of bourgeois economics a knowledge of the capitalist form of production, exchange and distribution is not alone adequate. We ought similarly to study at least in their essential features and taken as terms of comparison, the other forms which have preceded it in time, or exist alongside of it in less developed countries. Such an investigation and comparison has hitherto been briefly expounded only by Marx; and we owe almost entirely to his researches what we know about pre-bourgeois theoretical economics.' (ENGELS, _Antidühring_, p. 154). This was written by Engels twenty years ago; and since then the literature of economic history has grown remarkably, but historical research has been seldom accompanied by theoretical research. [30] 'Political economy is essentially an historical science.' (ENGELS, _l.c._, p. 150). [31] What is strange is that ENGELS (in the passage quoted in the penultimate note) says himself most truly that Marx has written _theoretical economics_, nevertheless in the sentence quoted in the last note (which appears in the same book and on the same page) he states definitely that economics in the Marxian sense is nothing but an _historical science_. [32] _Antidühring_, pp. 150, 155. [33] _Das Kapital_, I, p. 67. [34] F.A. LANGE, _Die Arbeiterfrage_, 5th ed., Winterthur, 1894, (the author's last revision was in 1874) see p. 332; _cf._ p. 248 and on p. 124, the quotation from Gossen's book, then very little known. [35] ADOLF WAGNER, _Grundlegung der politischen oekonomie_, 3rd Ed., Leipzig, 1892, vol. I, pt. I; Bk. I, ch. i. _Die Wirthschaftliche Natur des Menschen_, pp. 70-137.