The main reasons are located in the lack of attention to human beings as neighbours, to their living together, in the lack of historical consciousness, in the view that relations between creatures and God are accidental to God and the fact that the underlying metaphysics is substantial in stead of relational, and in the dominantly male horizon of thought. The author concludes that he and his colleagues hope to be brothers and sisters of Thomas, by theologizing according to Thomas' attitude towards society and new developments. He does so by reading Aquinas' treatise 'backwards', starting from concrete situations of justice and injustice which demand administration, which on its turn demands law. Human law is to be deduced from natural law, being the interpretation of man's nature as rational and applying the same arguments for himself as for others. This entails no deduction from the biological state of man, but an interpretation of his natural inclinations, and thus on what humans rationally deem good and evil.
Natural law is changeable inasmuch as it needs specification and articulation.
This also accounts for the diversity of human law, according to different times and places, different political and military rules. What different rules or peoples may have in common, Aquinas calls ius gentium. This 'unity in diversity' was replaced by the rise of modern states effecting a plurality of legal orders with sharp borders. Law becomes, in typical positivist understanding, a product of democratically legitimated rule, instead of rationality. However, new situations arise, in which such a conception no longer holds.