 Among fundamental categories, paired categories are the most general structural elements of being. As structural elements they have content, and there are composite relations among them (A23b). Hartmann organizes the various pairs into two groups of six pairs, without claiming that the list of paired oppositions is exhaustive. The first group includes principle-concretum, structure-modus, form-matter, inner-outer, determination-dependence, quality-quantity; the second group includes unity-manifoldness, harmony-conflict, opposition-dimension, discreteness-continuity, substratum-relation, element-complex. There is no intrinsic order among the pairs (A24a). It is apparent that some of these are easier to grasp than others. To provide a sample of Hartmann’s analysis, we now briefly describe two of the pairs, principle-concretum and element-complex (for more details see Werkmeister 1990, Poli 2011a, and A sections).