164 How detrimental it is to ignore the psychological nature of Political Economy is evident from the errors of _Karl Marx_, who personifies things in a manner almost mythological. Thus, according to him, modesty should be ascribed to a coat which exchanges for a piece of linen, and purpose to the linen, etc. (Das Kapital, 1867, I, 19, 22, seq.) The greatest fault of this intelligent but not very acute man, his inability to reduce complicated phenomena to their constituent elements, is greatly increased by his way of thus looking at things. 165 Compare _J. B. Say_, Traité I, introd. Thus, it would be certainly possible to describe every individual’s physiognomy by means of a very complicated mathematical formula, and yet there is no one who would not prefer the usual mode of taking pictures. The simple motions of the heavenly bodies, on the contrary, are always treated mathematically. (_Lotze_, Allgemeine Physiologie, 322 ff.) 166 When _Fawcett_ says that all “principles of Political Economy are describing tendencies instead of actual results” (Manual of Political Economy, 1863, p. 90), our method, the historical, would give also the theory of the latter. 167 This was lost sight of by most writers during the second half of the eighteenth century, because they looked upon that equality as the really oldest condition, and its restoration the ideal to be striven for. How much of this still clings to the present free-trade school; see in _Roscher_, Gesch. der N. Œk. in Deutschland, 10, 17 ff. 168 Thus, for instance, _Ricardo_ examines, almost exclusively, the actual condition of things, while the socialists confine themselves, still more exclusively, to the investigation of how things should be. It has been very usual in Germany since _Rau_ wrote, to draw a distinction between theoretical and practical Political Economy. There are many who think that a good manual of practical Political Economy, dropping the introduction, demonstrations etc., would be also a good code of law, of universal application. _Mercier de la Rivière_ has said that he wished to propose an organization which should be necessarily productive of all the happiness which can be enjoyed on earth. (Ordre essentiel et naturel (1767), Disc. prélim.) Compare, also, _Sismondi_, N. Principes, I, ch. 2.