Liebig’s analogy, based on an organic theory of the state, is crude, absent an analysis of money within the capitalist society. It is still interesting that the proponent of the concept of metabolism tried to connect physiology and political economy, a project soon taken up by Roscher and Marx.
Also, the agriculturalist in Munich, Carl Fraas, whom Marx intensively studied in 1868, emphasized the importance of “metabolism” for political economy: “Organism and metabolism—therefore, metabolism in the national economy, too! It builds the natural scientific foundation of national economy that was almost completely neglected until now in order to develop mere mathematical economics. However, such national economy only investigates and combines data without grasping their cause!”45 Even if there is no direct proof that Marx read Liebig’s Familiar Letters on Chemistry or Fraas’s article, it is conceivable, given the scientific discourse then, that Marx was also led to adopt this new physiological concept in his system of political economy.46
In the Grundrisse, there is one more usage of metabolism, the “metabolism of nature,” which proceeds independently of human intervention. Use values “are dissolved by the simple metabolism of nature if they are not actually used.”47 This “natural metabolism (natürlicher Stoffwechsel),” as chemical dissolution or modification of material substances, for example, occurs through oxidation and decomposition. Marx refers to this phenomenon again in Capital: “A machine which is not active in the labor process is useless. In addition, it falls prey to the destructive power of natural metabolism.”48 Labor alone cannot create natural substances; it can only modify their shapes according to various purposes. Labor provides the “natural substance” with “external form.”49
For example, the form of a desk that labor provides to the “natural substance” of wood is “external” to the original substance because it does not follow the “immanent law of reproduction.” Although the immanent law maintains the wood in its specific form of a tree, the new form of a desk cannot reproduce its substances in the same way, so that it now starts to get exposed to the natural force of decomposition. In order to protect the product of labor from the power of natural metabolism, a purposeful regulation of metabolism through productive consumption is required, which nonetheless cannot overcome the force of nature. Marx on the one hand emphasizes the human ability of labor to consciously and purposefully modify nature, but on the other hand he recognizes the inevitable limitations and restrictions imposed by nature on the human ability to control the metabolism of nature. He is aware of a certain tension between the immanent law of nature and the external form of nature artificially created by labor. The negligence of this material necessity results in decay and destruction of products by natural laws and natural forces.
To sum up, Marx in the Grundrisse employed the concept of metabolism of political economy with three different meanings and continues to do so until Capital: “metabolic interaction between humans and nature,” “metabolism of society,” and “metabolism of nature.” His sources of inspiration are not so apparent after his reading of Roland Daniels and Wilhelm Roscher because, following his own purpose of developing a system of political economy, Marx generalized and modified the concept as well. Precisely because of this generalization, Marx’s concept of metabolism is exposed to the risk of arbitrary interpretations, discussed together with irrelevant theorists, whose ideas actually have nothing to do with Marx’s theory of metabolism. In the earlier debates, one witnesses such cases that totally neglect Daniels and Liebig and focus only on the influence of “natural scientific materialists” (or “vulgar materialists” as Marxists often call them), such as Jacob Moleschott, Karl Vogt, and Ludwig Büchner. Such claims immediately sound very suspicious, considering that Marx referred to these authors only in private letters in a negative and pejorative tone.50 This misinterpretation shows the importance of correctly grasping Marx’s parting from Feuerbach’s anthropological materialism and the originality of Marx’s theory of metabolism, which must be understood not just philosophically but in a close relation to his system of political economy.
THE LIMITATION OF ANTHROPOLOGICAL MATERIALISM
Those who overvalue natural scientific materialism misinterpret not only Marx’s metabolism theory but also his entire project, because the theoretical affinity between Feuerbach and these natural scientific materialists often hides Marx’s non-philosophical, practical standpoint after The German Ideology. A typical misunderstanding of Marx’s project through the lens of Feuerbachian materialism and natural scientific materialism is characteristic of Alfred Schmidt’s famous book, The Concept of Nature in Marx: “It may be concluded with some certainty that Marx made use of Moleschott’s theory of metabolism, not, of course, without altering it.”51 Although Schmidt’s view is widely accepted, a careful examination of the texts makes his claim difficult to accept. There is no philological evidence for his claim; Schmidt and his admirers should have seen that Moleschott’s view, as elaborated in The Cycle of Life (Kreislauf des Lebens, 1852), is hardly compatible with Marx’s alliance with Liebig.52
Accordingly, Schmidt underestimates, perhaps intentionally, Liebig’s influence on Marx, but provides no convincing reason for doing so. In only one footnote, he succinctly refers to Liebig: “The chemist J. von Liebig, whose views were not without influence on Marx (cf. Capital, Vol. I, p. 506, n. 1), compared the metabolism in nature with the same process in the body politic, in his book Chemische Briefe, Heidelberg, 1851, p. 622 et seq.”53 Schmidt’s book does not go into Liebig’s Agricultural Chemistry because he believes that Marx “made use of the term ‘metabolism,’ which, for all its scientific air, is nonetheless speculative in character.”54 He clings to the philosophical concept of nature in the young Marx, no matter what it costs in terms of the truth. For Schmidt, Liebig is too “natural science” compared to Moleschott. However, it is not necessary to interpret the concept of metabolism in such a “speculative” manner, and Schmidt’s remark also contradicts the fact that Marx did not study various disciplines of natural science in accordance with a definite program of the philosophy of nature, as Hegel and Schelling did.
In order to ground his own claim, Schmidt quotes from Moleschott’s theory of metabolism in The Cycle of Life:
What man excretes nourishes the plant. The plant changes the air into solids and nourishes the animal. Carnivorous animals live on herbivorous animals, to fall victim to death themselves and so spread abroad newly germinating life in the plant world. The name “metabolism” has been given to this exchange of material.55
Moleschott’s explanation of metabolism, which is also expressed as “metempsychosis” among all material substances, is so general and abstract that one cannot immediately infer his influence on Marx’s theory.56 Thus it is necessary to look at Moleschott’s theory of metabolism more closely to judge whether Marx would be willing to integrate it “not, of course, without altering it.”
Moleschott was a Dutch doctor and physiologist who participated with Ludwig Büchner and Karl Vogt in a heated “materialism debate” in the 1850s. He advocated a radical materialist view that every mental activity is “only a function of substances in the brain,” and that “the thought stands in the same relation to the brain as bile to the liver or urine to kidneys.”57 Moleschott also reduced thought to a product of the movement of matter in the brain: “Thought is a movement of matter [Stoff].”58 While Liebig in his Agricultural Chemistry emphasized the importance of phosphoric acid for an ample growth of plants, Moleschott argued its importance for humans in a provocative manner: “No thought without phosphorus.”59 Admitting the necessity of further research on the functioning of the brain, he put forward a view that with the development of materialist physiology, both physical and mental activities and talents can be determined by measuring the assimilation and excretion of matter. In this vein, he argued that nourishment plays an important role in determining these activities. For example, he contrasted the English worker with the Italian lazzarone: “Who doesn’t know the superiority of the English worker