Man's social practice is not confined to activity in production, but takes many other forms--class struggle, political life, scientific and artistic pursuits; in short, as a social being, man participates in all spheres of the practical life of society. Thus man, in varying degrees, comes to know the different relations between man and man, not only through his material life but also through his political and cultural life (both of which are intimately bound up with material life). Of these other types of social practice, class struggle in particular, in all its various forms, exerts a profound influence on the development of man's knowledge. In class society everyone lives as a member of a particular class, and every kind of thinking, without exception, is stamped with the brand of a class.