I confess I used to think Natural Law theory was a lot of nonsense. But then I’m not sure I had really thought it through, influenced as I was by an evangelical Christian upbringing which meant that the assumption that all human beings were basically good (the synderesis principle) was wrong, as we are deeply flawed by human sin. I’ve changed my mind about that, but more particularly, here are three reasons to think more seriously about Natural Law.

1. We don’t have to accept the Roman Catholic version of Natural Law theory. I had failed to notice that the Natural Law of the Roman Catholic encyclicals such as Veritatis Splendour (see exerpt on the Natural Law section of the site) are fundamentally different from the Natural Law of Aquinas and the Greek concept upon which it is based. Veritatis Splendor (1995) presents secondary precepts as absolutes – as rules which can have no exception. So the Roman Catholic church has held out consistently against changing their view on abortion (application of the Reproduction primary precept) and contraception (application of the preservation of life precept) seeing these as unchangeable, fixed in stone. Under Pope Francis, of course, there are signs that this is changing, but no official declaration yet.

Yet Aquinas always stated that secondary precepts were ‘proximate conclusions’, essentially applications of our reason of the absolute and universal primary precepts. To present secondary precepts as absolute rules is a fundamental error – and one which students often make. A much subtler argument is this: the Roman Catholic Church from the 1960s declared war on relativism and began to expel liberal Catholic theologians such as Hans Kung. Against the ‘tyranny of relativism’ (Pope Benedict) they began to present a much harder version of Natural Law, and one which I personally don’t agree with.

2. Natural Law argues for provisional universals. This may sound like a contradiction, but in fact it is the only form of universal that makes sense. The claim to universality, correctly made by Veritatis Splendor, is based on the following logic. Natural law is rooted in naturalism, in the constitution of the world as it is. That is the world revealed to our reason by scientific and psychological enquiry. But you will have noticed that science is not static, and our understanding of ourselves has developed enormously with the insights of Freud or Jung in psychology or Stephen Hawking or Charles Darwin in science. In other words, our understanding of ourselves develops. We no longer think generally anyway that women are inferior to men or some people naturally condemned to a life of slavery as Aristotle argues.

But does this mean we don’t accept universal truth? Of course not. Medical students are told that in twenty years time half of what they’ve learned will have been proved to be false. Medicine used to believe as fact that stomach ulcers were caused by stress, until twenty years of insistence by an Australian doctor proved that they re caused by bacteria. The universal truth has changed because we can’t say that this makes the cause of stomach ulcers relative! It’s just that our understanding developed and with it, Natural Law.

3. Natural Law is flexible. Again it is quite wrong to see Natural Law as unchanging. Where we have a problem, of course, in that the primary precepts also seem to have subtly changed. For example, Veritatis Splendor no longer talks about worship of God as a primary precept but has widened the concept out into ‘appreciation of beauty’. Natural Law can do this because it is the application of reason to human ends – to rational goals that most of us (at least those who aren’t fanatics, or crazy) do agree are worthy of being ends. So it is reasonable to see the old formulation of worship of God as too narrow. What humans seem to share – everywhere and for all time, is a sense of curiosity and wonder at the state of the world and our own existence. This appreciation of beauty in a sunset, the wish to create great art and architecture, the passion for design and colour is something that makes human beings quite unique. It is central to our human flourishing, our ultimate goal of eudaimonia that we see beauty and stop and stare at it, feel the tinge down our spine and wonder – and it is that that pushes us towards the divine.