Martin Luther King Jr. is best known as a man of action. He didn’t merely write about injustice—he took to the streets, protesting racial “laws” that undermined the dignity of African-Americans. But unlike many current cultural protests we see today, King’s activism was grounded in something other than raw emotion or political impulse. He protested for a reason. In other words, he had a rational justification.
That justification was rooted in a moral principle he drew from St. Augustine: “An unjust law is no law at all” (De Libero Arbitrio [On Free Choice of the Will], book 1, chapter 5, sec. 11).
Martin Luther King Jr. explicitly appeals to this principle in his famous 1963 Letter from Birmingham Jail. Here’s the key passage:
One has not only a legal but a moral responsibility to obey just laws. Conversely, one has a moral responsibility to disobey unjust laws. I would agree with St. Augustine that “an unjust law is no law at all.”
Now, asserting a principle is easy. The harder—and more important—task is showing why it makes sense. So let’s do that here.
There’s a commonsense rule that guides almost every kind of human inquiry: you can’t spot a counterfeit unless you know the real thing. The same is true with laws. You can’t recognize a counterfeit “law” unless you first understand what a genuine law actually is.
To do that, it helps to turn to St. Thomas Aquinas, who explicitly affirms Augustine’s famous claim that “an unjust law is no law at all” (see Summa Theologiae I-II:96:4). Aquinas gives us a useful starting point with his definition of law.
He defines it as “a dictate of practical reason emanating from the ruler who governs a perfect community” (ST I-II:91:1). That may sound technical at first, but it’s easier to grasp once we break it down.
By “practical reason,” Aquinas means our intellect’s ability to know truth for the sake of action (ST I:79:11). This is different from what he calls speculative reason, which aims at knowing truth simply for its own sake, without reference to action.
A dictate of practical reason is simply the intellectual judgment that some behavior must be done—or avoided.
And when Aquinas speaks of “emanating from the ruler,” he just means that the person with authority must communicate those judgments to the community—essentially saying, “Do this, not that.”
Now, the binding nature of laws flow from two sources. The first is human nature. Our nature has an order of good built into it, shaped by our natural inclinations to acts and ends or goals that perfect us. Take the intellect, for example. It’s ordered toward knowing truth. When I know the truth, my intellect is perfected. And not just my intellect—I am perfected. Truth, then, is genuinely good for me, and my human nature is what makes it so.
This built-in order of good becomes the standard for evaluating human behavior. Behaviors that line up with what our nature identifies as good for us are morally good. Behaviors that clash with that order—actions that frustrate or undermine our flourishing—are morally bad.
Now, as Aquinas teaches, nature orders us to the good, such that we can’t choose anything unless we see it as good in some way (ST I-II:8:1). From this follows the most basic moral directive of all: do good, and avoid evil (ST I-II:94:1). This entire moral framework, rooted in the order of good inscribed in our nature, is what we call the natural moral law
The second source for the binding nature of law is proper authority. A ruler who truly has authority over a community can issue directives for the common good. For instance, as a father, I have real authority over my family and can require certain things for its well-being. Likewise, the president of the United States has legitimate authority to govern the nation and determine what should or should not be done for its good.
With all that in place, we’re now in a position to spot a counterfeit law.
Imagine that a ruler issues an edict that contravenes what is naturally good for us as human beings—something that directly violates the natural moral law. Suppose, for example, that a ruler declares that African-Americans may no longer participate in certain social activities because of their race, or are barred from pursuing an education. Such rules would run headlong into what human nature demands: perfection through the pursuit of truth and full participation in social life.
In cases like these, the edict loses its status as a genuine law. Why? Because the dictate of practical reason has broken away from what gives it binding force in the first place: human nature. Practical reason is ordered by nature toward discerning what leads to human flourishing. When it issues judgments that conflict with that end—judgments that oppose what is genuinely good for us—it forfeits its authority. Nature, after all, is prior to reason’s judgments. Reason is meant to conform to what nature requires for both individual and common good.
This gives us one clear way a “law” can cease to be a law: when it contradicts what is good for us as human beings—when it violates the natural moral law (ST I-II:96:1). In such cases, there is no obligation for the community to obey.
There’s another way a so-called law can lose its character. Suppose the ruler issuing the edict never legitimately acquired authority over the community in the first place. Lacking proper authority, he would have no right to command at all. And without that authority, his edicts simply wouldn’t qualify as laws. Remember, a law must emanate from a ruler who truly occupies a place of governance over the community. If that condition isn’t met, the supposed law lacks binding force, and the community is not obliged to follow it.
This brings us back to Martin Luther King Jr.’s claim that “one has a moral responsibility to disobey unjust laws . . . [since] an unjust law is no law at all.” In light of what we’ve seen, King’s moral reason is sound. The remaining question, then, is whether he applied that reasoning correctly in his particular situation.
I think he did. The “law” that King “disobeyed” was a Birmingham court injunction designed to squash civil rights protests in order to preserve racial segregation. Because that injunction upheld practices contrary to the human good—and actively prevented actions ordered toward the human good—it lacked the binding force of true law.
Although King’s refusal to comply with the court order was an act of “disobedience” with respect to the court, it was, at the same time, an act of obedience to what nature demands for the genuine good of human beings. And because God is the author of our human nature, obedience to that moral order is ultimately obedience to God.
For that reason, King’s actions were morally justified. What nature demands for the human good stands on a deeper level of reality—ontologically prior—than whatever a state authority happens to label as “law.”
In short, Martin Luther King Jr. got the philosophy right. And just as importantly, he got the practical judgment right about what needed to be done.