During the preparation of Capital, Marx intensively investigated this problem. He no longer propagated the realization of the philosophical idea of “humanism = naturalism” and instead tended more and more to describe the central task of the future society as the conscious regulation of this physiological metabolic exchange between humans and nature by the associated producers. This conceptual change is remarkable.
In this context, Michael Quante argues for the continuity of Marx’s philosophical conception of the relationship between humans and nature “even if Marx no longer describes it with anthropological and philosophical categories but with the natural scientific category of ‘metabolism.’”7 But then he criticizes both Marx’s “ambivalences” between philosophy and natural science and an “anti-philosophical trait” in Capital that is the result of this conceptual shift.8 However, Quante refrains from going into the new dimensions of Marx’s natural sciences in detail. Evidently his critique of Marx is grounded in his own interpretation, in which he hopes to rediscover the basic philosophical motives in the later economic works. The transition from a “philosophical” terminology to a “natural scientific” one is not a simple change of Marx’s personal preference, but reflects the development of his “materialist method” in The German Ideology as a guideline for understanding the historical transformations of the metabolism between humans and nature. In this sense, even if there is an “anti-philosophical trait” there are no “ambivalences” in his later works.
In contrast to the earlier philosophical scheme that simply imposes a utopian ideal on the estranged reality, Marx learned to analyze the concrete process between humans and nature, which is, on the one hand, transhistorical as an “eternal necessity,” but is, on the other hand, thoroughly socially mediated, given that the economic function of labor differs considerably in each mode of production. In The German Ideology, Marx became fully aware that the metabolic interaction takes place within a tight entanglement of both historical and transhistorical aspects. Marx carefully analyzed this dynamic social process in nature in order to comprehend the material conditions for transcending the “separation” in the metabolic interaction between humans and nature.
Marx’s research in the following years became more and more characterized by this unique duality. He studied political economy as an analysis of the social forms of economic categories, and simultaneously studied the natural sciences to achieve a scientific basis with regard to material qualities in the physical sphere. As emphasized in the following section, Marx’s ecology deals with the synthesis of the historical and transhistorical aspects of social metabolism in explaining how the physical and material dimensions of the “universal metabolism of nature” and the “metabolism between humans and nature” are modified and eventually disrupted by the valorization of capital. Marx’s analysis aims at revealing the limits of the appropriation of nature through its subsumption by capital.
This enormous project nonetheless cost Marx time and energy, so much so that he was not able to finish his magnum opus. Nonetheless, this does not mean that the project was a failure because Marx succeeded in elucidating his theory of metabolism in Capital and various economic manuscripts. Furthermore, there are a number of hints for his further theoretical development in his excerpt notebooks that are of great importance. Before analyzing these notebooks, it is helpful first to trace his own description of “metabolism” in the context of its usage in natural scientific and political economy.
ON THE GENEALOGY OF METABOLISM
The concept of “metabolism” was first employed in physiology at the beginning of the nineteenth century, even though it is often claimed that Liebig’s “book on Organic Chemistry in Its Application to Physiology and Pathology (1842) was the first formal treatise on the subject, introducing the concept of ‘metabolism’ (Stoffwechsel).”9 The famous German chemist is today known as the “father of organic chemistry”; along with Friedrich Wöhler he conducted a series of experiments to analyze chemical elements to find out not only that two molecules with the same molecular formula can have different properties (an isomer) but also that millions of different kinds of organic compositions can be formed out of various combinations of the simple and presumed unchangeable structures of organic compounds, even though their assumption of unchangeability later proved false.10 After 1837, Liebig conducted research in physiological chemistry and published the epoch-making Organic Chemistry in Its Application to Agriculture and Physiology, usually simply called Agricultural Chemistry, as the aforementioned Organic Chemistry in Its Application to Physiology and Pathology is usually called Animal Chemistry. In these books Liebig applied his newest discoveries in chemistry to an analysis of the organic process of plants and animals. He investigated the reciprocal relationship of plants, animals, and humans as chemical interactions of organic and inorganic substances, even claiming that “the animal organism is a higher kind of vegetable.”11 Liebig opened up the new field of chemical analysis of metabolism, which synchronized nicely with the newly discovered law of conservation of energy.12 He was highly critical of the dominant vitalist dualism of Jean-Baptiste André Dumas and Jean Baptiste Boussignault, who postulated the clear difference between “two kingdoms of plants and animals.”13
In one of the earliest usages of the term metabolism Liebig depicted the constant interactive process of formation, transformation, and excretion of various compounds within an organic body:
It cannot be supposed that metabolism in blood, the changes in the substance of the existing organs, by which their constituents are converted into fat, muscular fiber, substance of the brain and nerves, bones, hair &c., and the transformation of food into blood, can take place without the simultaneous formation of new compounds which require removal from the body by the organs of excretion.… every motion, every manifestation of organic properties, and every organic action being attended by metabolism, and by the assumption of a new form by its constituents.14
Metabolism is an incessant process of organic exchange of old and new compounds through combinations, assimilations, and excretions so that every organic action can continue. Liebig also maintained that the chemical reaction in combination and excretion is the ultimate source of electric current as well as that of warmth and force. Liebig’s theory of metabolism prepared a scientific basis for further analyses of a living organism as pure chemical process.15
The concept of metabolism, under the influence of Liebig, soon went beyond the nourishment of individual plants, animals, and humans. That is, it could be used to analyze their interaction within a certain environment. Today’s concept of metabolism can be applied not just to organic bodies but also to various interactions in one or multiple ecosystems, even on a global scale, whether “industrial metabolism” or “social metabolism.”16 This physiological and chemical concept about an extensive organic whole in nature found a wide reception and was employed beyond natural science, in philosophy and political economy, where it has been used to describe a social metabolism by way of analogy. This was the case in Marx’s writings. However, out of this extension there emerged a certain ambiguity due to the term’s multiple meanings, and it is necessary to distinguish them with commentary.
A careful conceptual differentiation of metabolism in Marx’s writings is of importance, for there are a number of debates in the earlier literature in terms of how he integrated this concept into his political economy.17 Even if it is difficult to determine every single source of his inspiration, given that he actively modified the concept for the purpose of his own analysis, this does not mean that one can use text in an arbitrary manner as a source for the sake of justifying a certain interpretation of Marx. Liebig is without doubt one of the most important intellectual sources, as has been convincingly demonstrated by John Bellamy Foster.18 The intellectual heritage of Liebig first became manifest in Capital. Yet Marx did not simply