The Natural-Scientific Foundation of Marx’s Concept of Labor

Labor is the key to understanding Marx’s thought. In the *Economic and Philosophic Manuscripts of 1844*, Marx understood labor as the objectification of man’s essential powers, and alienated labor as the expression of those essential powers within capitalist relations of production. This idea provided an important perspective for Marx’s later critique of capitalism. However, understanding Marx’s concept of labor cannot stop at philosophical categories such as alienated labor, objectification, and man’s species-being. In *Capital* and its related manuscripts, labor no longer appears as a purely speculative philosophical proposition; instead, it is placed within a synthesis of actual production, human bodily functions, material metabolism, and social forms. The deepening and development of Marx’s concept of labor cannot be separated from the empirical knowledge of the natural sciences, especially from the physiological explanation of human bodily functions.

劳动是理解马克思思想的锁钥。在《1844年经济学哲学手稿》中，马克思把劳动理解为人的本质力量的对象化，把异化劳动理解为这种本质力量在资本主义生产关系中的表达。这一思想为马克思后来的资本主义批判提供了重要的视角。但是，理解马克思的劳动思想，不能止步于异化劳动、对象化、人的类本质等哲学范畴。在《资本论》及其相关手稿中，劳动不再表现为纯思辨的哲学命题，而是被置于现实生产、人体机能、物质变换和社会形式的综合之中。马克思劳动思想的深化与发展，离不开自然科学的经验知识，尤其离不开生理学关于人体机能的阐释。

The natural-scientific foundation is not an over-interpretation imposed on Marx’s concept of labor by later generations. The young Marx had already paid attention to the natural sciences in the context of natural philosophy. From the 1850s onward, in his critique of political economy, Marx continuously followed the contemporary achievements of the natural sciences and persistently studied new works in agronomy, chemistry, geology, physiology, and other fields. Relevant excerpts were used in the writing of *Capital* and its related manuscripts. In the 1870s, Marx’s interest in the natural sciences surged; he delved into the interior of specific sciences, comprehensively and systematically reading, understanding, and absorbing the cutting-edge achievements of the natural sciences. The empirical knowledge of the natural sciences further confirmed Marx’s concept of labor. Thus, the natural-scientific foundation of Marx’s concept of labor has a solid documentary basis and is not a forced imposition by later generations. The natural-scientific foundation referred to here specifically denotes the empirical knowledge provided by disciplines such as physiology, medicine, physics, chemistry, agronomy, and geology. This knowledge influenced Marx’s concept of labor, making labor a real process with a physiological carrier, material conditions, and limits to reproduction.

自然科学基础并非后人强加于马克思劳动思想的过度解读。青年马克思曾在自然哲学语境中关注自然科学。19世纪50年代以来，马克思在政治经济学批判中持续关注同时代的自然科学成果，持续研读农学、化学、地质学、生理学等领域的新作。相关摘录被运用到了《资本论》及其相关手稿的写作中。19世纪70年代，马克思对自然科学的兴趣激增，深入到具体科学的内部，全面系统地阅读、理解和吸收自然科学的前沿成果。自然科学的经验知识进一步确证了马克思的劳动思想。由此可见，马克思劳动思想的自然科学基础有扎实的文献依据，并非后人的强行附会。这里所说的自然科学基础，特指生理学、医学、物理学、化学、农学、地质学等学科提供的经验知识。它们影响了马克思的劳动思想，使劳动成为有生理载体、物质条件和再生产限度的现实过程。

The subject of labor is concretized as the human being in the physiological sense

劳动主体落实为生理学意义上的人

A key advance in Marx’s concept of labor is the distinction between “labor” and “labor power.” What the capitalist buys on the market is not already completed labor, but the right to use labor capacity. Thus, the subject of labor is no longer merely the species-being in the philosophical sense, but a real body possessing physical strength, intelligence, sensory organs, neural coordination capacity, and physiological limits. This distinction enables Marx to explain why surplus value can still arise under the form of equivalent exchange.

马克思劳动思想的一个关键推进，是把“劳动”和“劳动力”区分开来。资本家在市场上购买的不是已经完成了的劳动，而是劳动能力的使用权。由此，劳动主体不再只是哲学意义上的类存在物，而是具有体力、智力、感官、神经协调能力和生理限度的现实身体。这个区分使马克思能够说明，在等价交换的形式下，为什么仍然能产生剩余价值。

Physiological and medical knowledge played a foundational role here. In *Capital*, when analyzing the value of commodities, Marx reduces different kinds of labor to the expenditure of human labor power, explicitly calling the expenditure of the brain, nerves, muscles, sensory organs, etc., a “physiological truth.” This is not an incidental turn of phrase, but a key step in the concretization of the concept of labor. Labor power is not an abstract will, but a unity of respiration, circulation, nutrition, metabolism, sensory reactions, neural conduction, and muscular movement. The worker can work continuously because the organism can mobilize energy, coordinate actions, and maintain the intensity of activity. The worker becomes fatigued, deteriorates, falls ill, and suffers injury precisely because this capacity has physiological boundaries. In this way, Marx goes beyond the early speculative formulations concerning man’s essential powers.

生理学和医学知识在此发挥了基础作用。《资本论》在分析商品价值时，把不同劳动化约为人类劳动力的耗费，明确把脑、神经、肌肉、感官等身体的耗费称为“生理学上的真理”。这并非偶然修辞，而是劳动概念现实化的关键。劳动力不是抽象意志，而是呼吸、循环、营养、代谢、感官反应、神经传导和肌肉运动的统一。劳动者能够连续工作，是因为机体能够动员能量、协调动作并维持活动强度。劳动者会疲劳、衰退、患病和损伤，正是因为这种能力有生理边界。由此，马克思超出了早期关于人的本质力量的思辨表述。

Of course, this concretization does not mean that Marx reduces “value” to a purely physiological expenditure. In his view, the objectivity of value can only take shape within capitalist commodity relations. The reason different private labors can appear as identical human labor in commodity relations is not that the differences between concrete labors disappear, but that these differences are abstracted away in the value relation. However, this social abstraction still requires the expenditure of human labor power as its real bearer. Therefore, the social form determines how this expenditure manifests as value, while the natural sciences explain how this expenditure actually occurs in human bodily functions. Physiology is not a substitute explanation for the value form, but an important condition for the concept of labor to acquire a real basis.

当然，这种落实并不意味着马克思把“价值”还原为纯粹的生理学耗费。按照他的看法，价值对象性只能在资本主义商品关系中形成。不同私人劳动之所以能够在商品关系中表现为同一的人类劳动，并不是因为具体劳动的差别消失了，而是因为这些差别在价值关系中被抽象掉了。但是，这种社会抽象仍然要以人的劳动力耗费为现实承担者。因此，社会形式规定这种耗费如何表现为价值，自然科学则说明这种耗费如何在人体机能中实际发生。生理学不是价值形式的替代解释，而是劳动概念获得现实根据的重要条件。

The labor process unfolds as a concrete material metabolism

劳动过程展开为具体的物质变换

Marx’s conception of “alienation” explains how man’s essential powers are externalized into objects in labor, and how, within specific capitalist relations of production, they evolve into a force that oppresses man. This idea shines with philosophical brilliance, but frankly, it lacks the necessary empirical support and has not been empirically confirmed. The relevant exposition in *Capital* overcomes this limitation. In Volume I of *Capital*, Marx further unfolds objectifying activity into the concrete labor process. In labor, man, according to a definite purpose, applies his own natural forces, with the help of instruments of labor, to change the form of natural objects, adapting them to human needs. The empirical knowledge of the natural sciences enabled Marx to see that labor is not a subject-centered activity without matter, but a real process constituted jointly by bodily capacities, natural objects, material properties, and means of production.

马克思的“异化”构想说明了人的本质力量如何在劳动中外化为对象，又如何在特定的资本主义生产关系中演变为压制人的力量。这一思想闪耀着哲学的锋芒，但坦率而言，它缺乏必要的经验支撑，在经验上尚未获得证实。《资本论》的相关论述克服了这一局限。在《资本论》第一卷中，马克思把对象性活动进一步展开为具体的劳动过程。人在劳动中按照一定目的，运用自身的自然力，借助劳动资料，改变自然物的形态，使之适应人的需要。自然科学经验知识使马克思看到，劳动不是没有质料的主体活动，而是身体能力、自然对象、物质属性和生产手段共同构成的现实过程。

In this process, knowledge of physics helps to understand force, motion, power, and energy transformation; knowledge of chemistry helps to understand material properties, fermentation, dyeing, and fertilizers; and knowledge of human physiology helps to understand sensory recognition, neural coordination, muscular movement, and labor intensity. On this basis, the labor process is not just the general schema of “the subject acting upon the object,” but a process of interaction among human organs, natural forces, material properties, and instruments of labor. In Volume I of *Capital*, Marx mentions that man can only function as nature itself does, i.e., can only change the form of matter. This judgment shows that Marx already recognized that labor is both a purposive activity and an activity conditioned by natural material circumstances.

在这一过程中，物理学知识有助于理解力、运动、动力和能量转化，化学知识有助于理解材料性质、发酵、染色和肥料，人的生理学知识有助于理解感官识别、神经协调、肌肉运动和劳动强度。基于此，劳动过程不只是“主体作用于对象”的一般图式，而是人体器官、自然力、物质属性和劳动资料相互作用的过程。马克思在《资本论》第一卷中提到，人只能像自然本身那样发挥作用，只能改变物质的形式。这一判断说明，马克思已然认识到，劳动既是有目的的活动，也是受自然物质条件制约的活动。

Large-scale machine industry makes this relationship particularly concentrated. Machinery can increase productivity and expand man’s domination over natural forces, but it can also, within the capitalist mode of production, damage nerves, suppress muscles, and subject the worker’s physical and mental activities to the rhythm of the machine. Benefiting from factory inspection reports and public health reports, Marx was able to advance the analysis of alienated labor from general philosophical relations to the concrete analysis of the factory system, labor intensity, machine discipline, and physical injury.

机器大工业使这种关系表现得尤为集中。机器可以提高生产率，扩大人对自然力的支配，却也可能在资本主义的生产方式中损害神经、压抑肌肉，使劳动者的身体和精神活动服从机器节奏。受益于工厂调查报告和公共卫生报告，马克思能够把劳动异化从一般哲学关系推进到工厂制度、劳动强度、机器纪律和身体损害的具体分析。

The limits of labor appear as the boundaries of the body and nature

劳动限度呈现为身体和自然的边界

Once labor is understood as the expenditure of living labor and a process of material metabolism, it necessarily possesses limits that cannot be arbitrarily transgressed. The analysis of the working day in *Capital* concentrates this point. The prolongation of the working day is, on the surface, a question of time, but in essence, it is the extended occupation of human life activity. The intensification of labor is, on the surface, a question of efficiency, but in essence, it is the more concentrated consumption of human bodily functions per unit of time. Sleep, diet, rest, air, sunlight, growth, and health are not life details outside economic relations, but necessary conditions for the reproduction of labor power. The reason Marx criticized the labor model of capitalist society is precisely that capital has long disregarded the limits of labor, repeatedly attempting to break through the production limits of man and nature.

劳动一旦被理解为活劳动的耗费和物质变换过程，就必然具有不可任意突破的限度。《资本论》关于工作日的分析，集中体现了这一点。工作日的延长，表面上是时间问题，实质上是人的生命活动被延长占用。劳动强度的提高，表面上是效率问题，实质上是人体机能在单位时间内被更密集地消耗。睡眠、饮食、休息、空气、阳光、成长和健康，并不是经济关系之外的生活细节，而是劳动力再生产的必要条件。马克思之所以批判资本主义社会的劳动模式，正是因为资本长期无视劳动的限度，试图一再突破人和自然的生产限度。

Marx’s understanding of production limits in Volume I of *Capital* partly originated from his natural-scientific reading in the 1850s and 1860s. However, he did not stop thinking about production limits after the publication of Volume I of *Capital*. After the French edition of Volume I of *Capital* was published, Marx immediately threw himself back into the study of the natural sciences, tracking new developments in physiology. In the spring of 1876, Marx systematically excerpted the physiological works of Schleiden and Ranke. Marx paid particular attention to cell metabolism, muscular movement, neural activity, fatigue, and recovery. The fatigue of cells and muscles is related to the decomposition products of chemicals; the blood circulation can carry away these products, restoring the muscles’ capacity to react. Stimulants can only temporarily eliminate the feeling of fatigue; they cannot replace the processes of nutrition and regeneration. This shows that Marx continuously used the latest physiological knowledge to consolidate his understanding of the expenditure, recovery, and reproduction of labor power.

马克思《资本论》第一卷中关于生产限度的认识，部分源自他19世纪50—60年代的自然科学阅读。但是，他并没有因为《资本论》第一卷的出版而停止思考生产限度问题。《资本论》第一卷法文版出版后，马克思又立即投入到自然科学的学习之中，追踪生理学领域的新进展。1876年春，马克思系统地摘录了施莱登和兰克的生理学著作。马克思尤其关注细胞代谢、肌肉运动、神经活动、疲劳与恢复。细胞和肌肉的疲劳同化学分解产物有关，血液循环能够带走这些产物，使肌肉恢复反应能力。刺激物只能暂时消除疲劳感，不能替代营养和再生过程。这表明，马克思持续用最新生理学知识巩固关于劳动力消耗、恢复和再生产的理解。

The limits of labor are also manifested in the reproduction conditions of nature. Agricultural labor is constrained by soil properties; soil fertility is the natural condition for the continuation of agricultural labor. Marx’s agronomic notebooks focus on issues such as soil mineral composition, land fertility, land depletion, fertilization systems, crop rotation, climatic conditions, and forest destruction. This natural-scientific knowledge constitutes the empirical basis for Marx’s reflections on the problem of ground rent and also influenced his thinking on agricultural labor. The analysis of ground rent in the third volume of *Capital* also shows that agricultural labor cannot rely solely on empirical custom but must consciously apply the scientific theories of agronomy. In this sense, the difference between agricultural labor and industrial labor lies in the fact that agricultural labor must attend not only to the physiological boundaries of human beings but also to the natural limits of the land. The more capitalist production treats labor power and land as elements that can be used without limit, the more it reveals its own dual plunder of workers and natural conditions.

劳动的限度还体现为自然界的再生产条件。农业劳动受限于土壤性质，土壤肥力是农业劳动得以持续的自然条件。马克思的农学笔记关注土壤矿物成分、土地肥力、土地耗竭、施肥制度、作物轮作、气候条件和森林破坏等问题。这些自然科学知识是马克思思考地租问题的经验基础，也影响了马克思关于农业劳动的思考。《资本论》第三卷关于地租的分析也显示，农业劳动不能单纯依靠经验惯例，而是应该自觉运用农学的科学理论。在这个意义上，农业劳动和工业劳动的差异就在于，农业劳动不仅要关注人的生理边界，还要留意土地的自然限度。资本主义生产越是把劳动力和土地当作可以无限使用的要素，越会暴露出自身对劳动者和自然条件的双重掠夺。

In summary, it is precisely because of the empirical support of the natural sciences that Marx’s critique of capitalist society avoids empty humanism and avoids treating human labor as a pure form without a body, without nature, and without an empirical foundation. Re-understanding this point today helps us to understand and respect labor in a more concrete way. Respecting labor means not only praising labor for creating wealth but also respecting the life capacity, health conditions, skill development, and creative potential of the laborer. Genuine labor emancipation means making production development serve the all-round development of human beings, and making the natural sciences, technological progress, and social systems jointly point toward the enrichment of human life capacity.

综上所述，正因为有了自然科学的经验支撑，马克思对资本主义社会的批判才能避免空洞的人本主义，才能避免把人的劳动处理成无身体、无自然、无经验基础的纯粹形式。今天重新理解这一点，有助于更加具体地理解并尊重劳动。尊重劳动，不只是赞美劳动创造财富，更是尊重劳动者的生命能力、健康条件、技能发展和创造潜能。真正的劳动解放，意味着使生产发展服务于人的全面发展，使自然科学、技术进步和社会制度共同指向人的生命能力的丰富。

(The author is a lecturer at the School of Philosophy, Beijing Normal University.)

（作者系北京师范大学哲学学院讲师）