This chapter explores the relationship between man and nature as well as man and society, revealing the dynamic changes of these relationships in historical development and their profound significance for human emancipation. Marx critiques Feuerbach’s simplistic view of the relationship between man and nature as merely one between natural objects, emphasizing that labor transforms nature into “humanized nature,” while alienated labor under private ownership leads to “alienated nature.” In terms of the relationship between man and society, Marx argues that private ownership causes individuals to lose their social essence, becoming “unsocial man,” whereas communism, through the abolition of private ownership, enables individuals to reclaim their social essence and realize the return of “social man.” By integrating practice with labor, Marx transcends the abstract understanding of practice in traditional philosophy, unveiling the essence of labor as a material and social activity. He particularly highlights how natural science, through industry, transforms human life. Though it exacerbates alienation under capitalism, it lays the foundation for human liberation. Ultimately, Marx predicts the unification of natural science and the science of man into a single discipline, a view that has been substantiated by modern interdisciplinary integration. This chapter demonstrates how Marx, starting from labor practice, constructs a framework of the materialist view of history that dialectically unites man, nature, and society.