 Principle-Concretum: Concretum for Hartmann is what is determinate, that in which categories are embedded as their determinations. The concretum is not limited to real entities, but includes ideal ones as well. Furthermore, the concretum for Hartmann is not to be understood as limited to the individual instances of a principle because there can be different levels of concreta. For instance, strata categories are concreta with respect to general categories. In this case, both the concretum and its principles are categories. Real categories contain all the universal determinations of their concreta; they contain what is needed for the structure of the concreta. A complete system of categories—not the incomplete one we are able to grasp—completely determines its concreta (A4a). As natural laws exist only in the real processes of nature and are nothing outside of them, so real categories exist only as structural relations within the real world and are nothing in themselves (A16c). The principle-concretum form of determination is only one among a variety of types of determination, and in no way is it the most relevant in the real world. In fact, each real level has its own specific types of determination, such as the specific linear nexus (causal, final, etc.) that unifies the phases of the processes that unfold within and between concreta. In sum, principles are that through which the concretum is (partially) grasped. They are the archai of the concretum, the condition of its possibility or that on which the concretum rests. They have unconstrained validity for all the concreta that fall within their range (A27c).