Like Aristotle, Aquinas concludes that humans aim for some goal or purpose, but does not see this as eudemonia which Aristotle saw as the final goal for humans (supreme happiness/good). Humans for Aquinas are above all made “in the image of god” and so the supreme good must be the development of this image i.e. perfection. However unlike Aristotle, Aquinas did not think that this perfection was possible in this life. For Aquinas, Natural Law i.e. the theory that an eternal absolute moral law can be discovered by reason which is a reflection of Gods eternal law which is also reflected in divine law i.e. the bible.
Aquinas thought that god had instilled in all humans (intrinsic) inclinations to behave in a certain way which leads us to the highest good and, by using our reason, we can discover the precepts (laws) which express God’s Natural Law built into us. Aquinas saw the primary precepts of Natural Law as always true and applying to everybody without exception because we all have this innate nature, and as they are a direct reflection of God’s Eternal Law i.e. the principles by which God made and controls the universe which are only fully known by God. The primary precepts are as follows:
- The preservation of life
- Reproduction
- The nurture and education of the young
- Living peacefully in society
- To worship God
These primary precepts are always true in that they point us in the right direction and are necessary for human flourishing.
The secondary precepts, on the other hand, are dependent on our own judgements of what actually to do in a given situation and are open to faulty reasoning and may lead to completely wrong choices, this makes them more teleological than deontological. The secondary precepts require experience, the use of reason and the exercise of wisdom. The secondary precepts make Aquinas’ understanding of Natural Law realistic and flexible. It does not imply a body of principles from which we simply work out our moral decisions, but takes into account our human limitations and weaknesses. Natural Law may seem rigid but the secondary precepts have to be interpreted by in the context if the situation. You cannot simply read the secondary precepts from the primary precepts like a list of instructions; so, for example the primary precept of reproduction might need secondary precepts that explain what is acceptable sex and what is an acceptable way to have children e.g. IVF
The most fundamental intrinsic inclination for humans, according to Aquinas is to act in such a way as to achieve good and avoid evil. Aquinas saw in fact humans do not always behave like this and explained this by saying that we got things wrong and followed apparent good i.e. something we think is good but in reality does not fit the perfect human ideal for example if someone has an affair they do not intend to hurt their partner but because they think there ‘in love’ than this is the right thing to do. In order to work out what is a real good and what is an apparent good we need to use our reason correctly and choose the right thing to do, (‘right use of reason’ as Aquinas called it) to work out what to do.
