In the course of the letter, Dr. King justifies his principles according to the differentiation between ‘just’ and ‘unjust’ law, as it is arbitrarily difficult to logically defend an unjust law. Yet what exactly is an unjust law? To find a solution to this moral problem, he understandably turns to that great Christian apologist, St. Thomas Aquinas. King paraphrases Aquinas, saying, “An unjust law is a human law that is not rooted in eternal law and natural law.” This is a misleading construction of Aquinas’ position, which deserves a closer inspection than what Dr. King supplies.
Aquinas, in his Summa Theologica, recognizes four legitimate forms of law:
a. Eternal Law
b. Natural Law
c. Human Law
d. Divine Law
It should be noted that Natural, Human, and Divine Law are all essentially branches of Eternal Law. Aquinas defines Eternal Law as “the type of Divine Wisdom, as directing all actions and movements” (Summa, Q. 93), or the universal laws by which God governs the universe. Aquinas divides Natural Law, or Eternal Law that may be identified through natural human reason, into precepts, the first being “that good is to be done and ensued, and evil is to be avoided,” and “all other precepts are based upon this” (Q. 94). Human Law is the law created by humans to promote Natural Law, while Divine Law is law revealed by God through the Bible.
I. With Aquinas’ explanation of Eternal Law comes Dr. King’s first misrepresentation. As Aquinas explicitly states in Q. 93:
Human law has the nature of law in so far as it partakes of right reason; and it is clear that, in this respect, it is derived from the eternal law… Even an unjust law, in so far as it retains some appearance of law, though being framed by one who is in power, is derived from the eternal law; since all power is from the Lord God.
Clearly, Aquinas believes that even an unjust law must originate from Eternal Law. Dr. King’s paraphrase of Aquinas, which concludes that unjust laws are not rooted in Eternal Law, is therefore false.
II. King’s paraphrase of Aquinas might secondly lead the reader to conclude that those laws not associated with the Natural Law are unjust. This is at first consistent with Aquinas’ position, but not arbitrarily true on closer inspection. As Aquinas asserts in Q. 94:
We may speak of virtuous acts in two ways: first, under the aspect of virtuous; secondly, as such and such acts considered in their proper species. If then we speak of acts of virtue, considered as virtuous, thus all virtuous acts belong to the natural law… But if we speak of virtuous acts, considered in themselves, i.e. in their proper species, thus not all virtuous acts are prescribed by the natural law: for many things are done virtuously, to which nature does not incline at first; but which, through the inquiry of reason, have been found by men to be conducive to well-living.
In summary, virtuous acts do not always belong to Natural Law. It logically follows that laws may exist which promote virtuous acts but at the same time are not rooted in Natural Law. King was nonetheless correct in stating that unjust laws (laws which do not promote “common good”) can not be rooted in Natural Law.
Certainly Dr. King was a commendable figure and intelligent writer, but gave too brief a summary of Aquinas’ complex position in order for it to have been fully accurate.