It has been said that the question of universals was the question of the Scholastics. Sadly, it seems to have ended with the winner (at least as far as unaware secular society is concerned) being the nominalism of Ockham (which I would attribute the beginnings of his errors to Scotus, as I believe our current Pope did in a lecture some time back).
After reading Servias Pinckaers’ masterpiece The Sources of Christian Ethics, I had been enlightened into how this rejection of universals (for all practical purposes) forever changed the world’s outlook on morals and made God (if He still existed) into an arbitrary dictator at best.
Certainly, in the realm of natural law, it will be hard to justify the truth of natural law as related to human nature if no such thing as human nature can be affirmed.
In my theological and philosophical studies, probably no single sentence has affected me more than one written by Ettiene Gilson in his book The Unity of Philosophical Experience:
When and where piety is permitted to inundate the philosophical field, the usual outcome is that, to better extol the glory of God, pious-minded theologians proceed joyfully to annihilate God’s own creation (pg. 30)
However, the Catholic position, rightly taken from the encyclical Faith and Reason, is well stated here:
The unity of truth is a fundamental premise of human reasoning, as the principle of non-contradiction makes clear. (notice the appearance of the important foundation of non-contradiction) Revelation renders this unity certain, showing that the God of creation is also the God of salvation history. It is the one and the same God who establishes and guarantees the intelligibility and reasonableness of the natural order of things upon which scientists confidently depend, and who reveals himself as the Father of our Lord Jesus Christ. (34)
Ockham seems to me to have been one such “pious-minded theologian.” The result has been a separation of faith and reason. We can no longer affirm natural law. We can no longer say that is implies ought. The secular world has had a field day with this. On the other side, especially among the reformers and those who follow the protestant tradition, every truth must now come from the Bible, and reason is looked upon with suspicion.
Fr. Coplestone points out what happened quite clearly:
Of course, in all medieval systems of thought the uniformity and regularity of natural processes were regarded as contingent in as much as the possibility of God’s miraculous intervention was admitted by all Christian thinkers. But the metaphysics of essence had conferred on nature the comparative stability to which Ockham deprived it. With him relations and connections in nature were really reduced to the coexistence or successive existence of absolutes. And in the light of the divine omnipotence, believed on faith, the contingency of relations and of order in nature was seen as the expression of the all-powerful will of God. (History of Philosophy Vol. III)
All sorts of philosophies have followed this arbitrary connection between God’s creation and what it does, such as occasionalism, etc. We see it in Descartes’ (almost fictional) connection between the mind and the body. We see it leading to both empiricism and idealism, depending on its interpreter. But the point is, if universals are not something that is truly objective in “the things themselves,” we either have an arbitrary God or no god at all; neither is conducive to establishing natural law.