As a philosophical concept, value pertains to an essential dimension of the relation between subject and object, one of those basic relations pervading human society. To understand value, we need first to clarify the concept of subject and that of object, to reveal the interaction between subject and object. It involves making a generalization of those substantial relations between subject and object, in order to understand the nature of value. This would make the argument in this book to be abstract and contemplative in some places, but full of concrete details in others.