Abstract: As a critic of the bourgeoisie ideology and a rival of the capitalist system, socialism should not only eliminate material poverty and labor enforcement by developing productivity, but also realize the ideal of both individual development in an all-round way and the free union of individuals by reforming social system. However, traditional socialist theories focus too much on the former while ignore the latter. While inheriting the enlightenment tradition of the bourgeoisie, German classical philosophy goes beyond the limitation of utilitarianism in the enlightenment tradition of England and France by clearly regarding freedom at the level of self-determination as the core of human liberation. Inheriting the principle of individual autonomy in German classical philosophy, Marx maintains that human freedom does not equal to knowing nature and controlling the production process; on the contrary, it should be understood as the development of human beings themselves and their co-control of the production process. Although he claims that the development of human ability to know and change nature is indispensable for human liberation, Marx emphasizes that the realm of freedom is actually on the other shore of labor and the realm of necessity. In other words, we can achieve real freedom only in voluntary activities aiming to develop ourselves. This conceptual distinction between cognitive freedom and practical freedom, and the recognition that the latter is prior to the former should be confirmed again as the core and foundation of socialism in the 21^st century. Under the guidance of the development ideal of "regarding people as the center", the practice of socialism with Chinese characteristics in a new era will demonstrate that socialism is essentially the great course of human liberation.

Key words: practical freedom, cognitive freedom, Kant, Hegel, Marx, socialism