Thomas Aquinas developed a comprehensive framework dividing law into four types—eternal, natural, divine, and human—to show how God works through all things, despite human sinfulness, to achieve his purposes for humanity.

David McIlroy explores Thomas Aquinas’s systematic framework of natural law, examining how the medieval philosopher believed moral principles are known through reason and natural human inclinations at three distinct levels.

David McIlroy examines how legal positivism—the approach to law that focuses on whether legislation comes from the right source rather than its moral content—has roots in thinkers like Hobbes, Bentham, Austin and Hart, and explores Amanda Perreau-Saussine’s argument that all consistent legal positivists ultimately reject any philosophical notion of moral authority.

This sixth post in our Legal Theory in Brief Series explores the famous Hart–Fuller debate over whether law possesses an “inner morality,” contrasting Hart’s claim that even immoral regimes can create valid law with Fuller’s argument that true law requires adherence to moral procedural principles that enable human agency and justice.

In this fifth post in our Legal in Brief Series, David McIlroy explores and contrasts H.LA. Hart’s notion of Rules with Wesley Hohfeld’s notion of Rights and their implications for law.

In this fourth post and video in the series, David McIlroy explores John Locke’s conception of Rights and Authority, and shows how they have shaped our idea of rights and authority in modern society.

In this third post in our series, Legal Theory in Brief, David McIlroy examines the different meanings and defining features of law, contrasting checklist and central case approaches to understanding what truly makes a rule a “law.”