Abstract:In his early Economic and Philosophical Manuscript of 1844, the alienation of labor products, the alienation of labor process, the alienation of human Gattungswesen, and the alienation between people constitute the basic definitions of Marx’s theory of alienated labor. These definitions are both different and related, and can neither be confused nor discarded.In the history of thought, Hegel proposed the alienation theory of “self-awareness” as the essence of the world spirit, while Feuerbach proposed the alienation theory of human “prior essence”. The common ground of the two is that they both view alienation as the loss of a predetermined prior essence, and overcoming alienation means the reacquisition (i.e. restoration) of this prior essence. Marx regarded labor as a free and conscious activity and the essence of human beings, the loss of human (labor) essence and the reduction of people to “non-human” are therefore the core and essence of Marx’s theory of alienated labor. Moreover, this theory has the function and significance of explaining paradigms.In contrast, in his mature works German Ideology and On Capital and its preparation manuscripts, Marx retained and continued to use the concept of alienation, but it no longer means a “non-human” state that renders people incapable of being human but rather a description of specific individuals in specific situations in reality. In this sense, alienated people are also a type of persons reflecting the essence of a person. Human labor, whether free or not, conscious and intentional or unconscious and spontaneous, all reflex and reflect the essence of human reality. Alienation is no longer related to the transcendental nature of human beings, and the alienation theory no longer has the role and significance of explaining paradigm. Instead, it is a historical materialism that reveals the movement law of basic social contradictions.Real people are not “human” but “human” is not real, which is a theoretical dilemma that the alienation labor theory is difficult to overcome. When a person is a real person, he is not human but “non-human”; when a person exists as “human”, he is not a “real” existence or rather lacks reality.From this perspective, the so-called “existentialist” interpretation of the decomposition of alienated labor into labor alienation and life alienation is questionable. It confuses alienation as separation, putting aside the presupposition and loss of human prior essence to discuss alienation and labor alienation. The understanding of the concepts such as labor and nature, or the understanding of the relationship between nature and labor products, as well as the various definitions of alienated labor, are all inconsistent with Marx’s thought. It overlooks the rupture that occurred between Marx’s early theory of labor alienation and the concept of alienation in the mature period.