If you were to use Thomas Aquinas’s ‘Natural Law’ as an example of a deontological system, you would want to bear in mind the following:

• A deontological system of ethics treats certain acts as morally wrong under all circumstances.

• Somewhat infamously, the AQA Specification uses Aquinas's 'Natural Moral Law' as an example of a deontological system.

• Many (if not MOST) scholars would say that Aquinas ACTUALLY teaches a flexible system of virtue ethics.

• Indeed, even the official AQA textbook notes this error (Frye 2017: 121)

• However, if you are doing AQA, you CAN use Aquinas as your example of a ‘deontological’ system.

• The following explains how to draw out Aquinas's more deontological qualities.

The Synderesis Principle

• Aquinas begins by explaining ‘The good is what all things desire. Therefore, the first precept of law is that good ought to be done and pursued and that evil ought to be avoided’ (ST I-II, Q. 94, Art. 2).

• He means that everyone naturally seeks ‘the good’.

• People might be confused about what that is, but everyone chases whatever seems ‘good’ to them — it is not possible to seek evil for yourself.

The Primary Precepts

• Aquinas identifies three natural human desires.

• These are the things everyone knows as ‘good’:

  • Physical — the desire to exist (preservation of life)

  • Biological — the desire to make children (reproduce) and raise children (education of the young).

  • Rational — the desire to live with others (ordered society) and understand God (praise God).

The Deontological Angle

• This is the ultimate deontological system, because these precepts literally cannot be broken.

• As Aquinas explains ‘there is the same truth or correctness for everyone and it is equally well known to everyone’ (ST I-II, Q. 94, Art. 2).

• In other words, everyone knows these precepts are ‘good’ and tries to achieve them.

• Debate only happens when people disagree about how to do this.

References

• Aquinas, Thomas. n.d. 'New English Translation of St. Thomas Aquinas's Summa Theologiae (Summa Theologica)', trans. Alfred J. Freddoso <https://www.freddoso.com/summa-translation/TOC.htm> [accessed 02 June 2026]

• Frye, John. 2017. 'AQA A-Level Religious Studies' (Hodder Education)