Thomas Aquinas: the natural law

justice1To most people in the modern era the concept of natural law is nebulous and fuzzy. This is largely due to a fundamental difference between modern and classical/medieval philosophy, but more on that later.

In the Aristotelian tradition within which medieval philosophers such as Aquinas worked, natural substances have essences or natures – that is to say they possess a formal and final cause. These formal and final causes direct the substance toward certain natural ends. For example, the natural end of a tree is to undertake photosynthesis. The tree which absorbs nutrients and water from the ground through its roots and sunlight through its leaves is a good tree; conversely a sick tree who cannot perform these actions is a bad tree.

Thus under this view , goodness is simply a natural substance being reduced in potentiality to actuality according to its form and end. However, in human beings this scheme takes on a notably different character, a moral character. People are different from trees and other animals because of their rationality, and as such are distinctly moral agents.

Aquinas famously sums up natural law as a self-evident principle “that good is to be pursued and evil avoided”. Aquinas argues that it is self-evident that in every choice we choose according to some perceived good or ill. Following that, because man is rational he is capable of perceiving the ends that are set forth for him by his essence. In this way, Aquinas stands in stark contract to the skeptic Pyrrho. Aquinas then concludes that the final cause of the intellect and reason itself is the pursuit of truth and goodness.

But why is natural law not considered relevant in our modern time? This is because of the mechanistic and atomistic nature of the modern Cartesian view of the cosmos. According to this philosophy, there are no essences, natures, forms or final causes. As such, what is good for man becomes a matter of social convention.


9 responses to this post.

  1. […] the previous post, I examined Aquinas’ thesis of natural law. It was mentioned that man differs from animals on account of the moral character endowed by his […]


  2. […] to his voluntarism, Scotus’ views on natural law were  in stark contrast to those of Aquinas. For Aquinas, God’s reason is primary and the […]


  3. […] first glance that there were limitations upon God’s power. For example, according to Aquinas the nature of man causes the act of murder or adultery to always be bad for us – and there can be no way for God to change that. Per Aquinas this is not a real limitation […]


  4. […] what are natural rights? It is important to delineate them from natural law. Generally speaking, when discussing natural law writers tended to focus on duties that applied to […]


  5. […] this way, Hume stands in stark contrast to the natural law theorists of the medieval times. For thinkers like Aquinas, it is possible through an empirical analysis of a substance to come to […]


  6. […] Hume was arguably the most influential hand in the modern periods discounting of natural theology. For scholastic writers, such as Aquinas, an effect is necessarily conjoined to its cause and thus […]


  7. […] Kant’s radical departure from the natural law of medieval philosophy. According to natural law, what is good for a substance depends upon its […]


  8. […] upon positive law (where the state is the ultimate law-giver and law enforcer) rather than the natural law of Aquinas or the natural rights of […]


  9. […] as he pleases. This similar to Kant’s thesis of man as self-legislator, and in contrast to a natural law thesis under which man’s nature determines what is good for […]


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