Thomas Aquinas: Natural Law, Validity, and Legal Efficacy

Legal Philosophy: Justice, Validity, and Efficacy

The relationship between justice, validity, and the effect (efficacy) of law is central to legal philosophy.

Some argue that if a legal standard does not comply with justice, it should not be compulsory, and therefore should not be considered valid. However, this argument is often rejected by those who state that the validity or enforceability of the law is independent of its justice or injustice. They assert that the law is valid simply because the standard has been created by man, usually under the authority of the State.

Alongside these notions is Efficacy (or effectiveness), which means that the legal standard is met in practice. This occurs either because the addressee of the rule obeys it inadvertently, or because the authority enforces sanctions, ultimately implementing the rule by force.

The Doctrine of Natural Law in Thomas Aquinas

The most important work by Thomas Aquinas is the Summa Theologica, where he proposes his doctrine of natural law and natural right (Droit).

Distinguishing Law (Lex) and Right (Ius)

St. Thomas distinguishes between Law (Lex) and Right (Ius). Generally speaking, the Law is a rule that regulates behaviors. However, Right (Droit or Ius) is a righteous act, an act of justice, or as he prefers to say, the Right is the right thing.

The Four Categories of Law

Aquinas refers to four distinct kinds of laws:

• Divine Law

  This is the law revealed in the scriptures, specifically the Bible. Its content is wide and varied.

• Eternal Law

  The Eternal Law is God himself. It cannot be fully disclosed because it is infinitely greater than the human mind. We know only partial manifestations of it in our consciousness, and these partial manifestations are what St. Thomas calls Natural Law.

• Natural Law

  This is a partial manifestation of the Eternal Law in the conscience of man. Its great principle is to do good and avoid evil. Men can distinguish between good and evil because we possess a faculty called synderesis in our consciousness that allows us to make this distinction. According to St. Thomas, Natural Law has three key features:

  1. It is knowable.
  2. It is indelible.
  3. It is universal.

• Positive Human Law

  Positive Human Law must be subject to Natural Law and derives from it. In the Summa Theologica, it is defined as "an ordinance of reason for the common good, promulgated by him who has the care of the community." St. Thomas holds that positive law contrary to natural law is not binding in conscience; that is, it can even be flouted.