Principles exhaust themselves and are nothing in themselves

 The two main aspects of categories are their generality and their character of determination. The latter is the feature that makes them principles. Principles exhaust themselves in this determining role. Principles are nothing in themselves. They only exist for something else; they are something only with respect to the concretum (contrasted with abstraction) .that they determine and are in. Principles are nothing without their concretum, and the concretum cannot exist without its principles.