What Is Law? Hart, Fuller, and Dworkin

There is a question that sits underneath every other question in legal philosophy, and it is surprisingly rarely asked directly. Not what should the law do, or how should the law be interpreted, or whether a particular law is just. The question underneath all of those is simpler and stranger: what is law, actually? What kind of thing is it? Where does it come from and what gives it the authority it claims?

Three thinkers in the twentieth century gave answers to that question that changed the field permanently. H.L.A. Hart argued that law is a system of rules, and that the question of what law is should be kept strictly separate from the question of what law ought to be. Lon Fuller argued that law has an inner morality built into its very structure, that certain procedural requirements are not just good ideas but constitutive of what law even is. Ronald Dworkin argued that law is not just rules but principles, that judges are always doing moral reasoning whether they admit it or not, and that the right answer to legal questions is usually a moral answer dressed in legal clothing.

All three of them are reaching for something real. None of them, I think, gets all the way there. And the place where they fall short points toward something worth saying.

Hart: The Separation Thesis

Hart’s central claim, developed in The Concept of Law (1961), is that law and morality are conceptually separate. A law can be valid without being just. A law can be unjust without ceasing to be law. The question of what the law is and the question of what it ought to be are different questions, requiring different kinds of analysis, and conflating them produces confusion in both directions.

This is a clarifying move and Hart makes it well. There is real value in being able to say: this law exists, it was validly enacted, it is being enforced, and it is also morally wrong. Keeping those claims separate allows for a kind of honesty that muddier theories do not. It allows critics of unjust laws to say exactly what they mean without having to argue that the law in question somehow fails to count as real law.

But the separation thesis has a cost. If law is simply a system of rules validated by other rules, with no necessary connection to moral truth, then law’s claim to obedience becomes purely procedural. You should follow the law because it was made the right way, not because it is tracking anything real about justice. And that feels insufficient — not just emotionally but philosophically, because it leaves unanswered the question of why procedural validity should generate any obligation at all. Hart can tell you what law is. He struggles to tell you why it matters.

Fuller: The Inner Morality of Law

Lon Fuller’s response to Hart, developed most fully in The Morality of Law (1964), is that the separation thesis misunderstands what law is. Law is not just any system of rules. It is a purposive enterprise — an attempt to subject human conduct to the governance of rules — and that enterprise has internal standards that are genuinely moral in character.

Fuller identified eight principles he called the inner morality of law: generality, promulgation, non-retroactivity, clarity, non-contradiction, possibility of compliance, constancy, and congruence between official action and declared rule. A system that systematically violated these principles would not just be a bad legal system. It would fail to be a legal system at all, because law is constitutively committed to governing through rules in a way that respects the agency of those governed.

This is a more attractive picture than Hart’s in some ways. It builds moral content into the definition of law itself, which means law cannot be entirely indifferent to justice without ceasing to be law. And Fuller’s procedural morality does track something real: there is a meaningful difference between a society governed by clear, stable, publicly known rules and one governed by arbitrary decree, even if both are unjust by some external standard.

But Fuller’s inner morality is thin. It is a morality of procedure, not substance. A legal system can satisfy all eight of Fuller’s criteria and still be deeply, systematically unjust. Apartheid South Africa had clear, promulgated, consistently applied rules. The rules were monstrous. Fuller’s framework tells you something about the form law must take. It tells you very little about whether the content of the law is good.

Dworkin: Law as Integrity

Ronald Dworkin thought both Hart and Fuller were missing something essential. In Taking Rights Seriously (1977) and Law’s Empire (1986), he argued that law is not just rules and not just procedures. It is a practice of interpretation, guided by principles, aimed at presenting the community’s legal history in its best moral light.

On Dworkin’s view, judges are not just applying rules when they decide hard cases. They are doing moral reasoning, whether they acknowledge it or not. The best legal decision is the one that fits the existing body of law while also justifying it in moral terms, showing how the law, understood correctly, expresses a coherent set of principles that a just community could endorse. Dworkin called this ideal “law as integrity,” and he imagined it embodied in a hypothetical judge of superhuman wisdom and patience he called Hercules.

Dworkin is, of the three, closest to something I find genuinely compelling. The insistence that legal reasoning is always also moral reasoning, that you cannot cleanly separate the interpretation of law from questions about what justice requires, feels true to me. It matches the way legal argument actually works. And the idea that law should be understood as an ongoing interpretive practice, not just a static set of commands, captures something Hart’s picture misses entirely.

But Dworkin’s theory has a problem that he never fully solves, and it is a serious one. It depends on judges having a kind of moral wisdom that makes them reliable interpreters of the community’s best moral commitments. And that dependence is philosophically questionable in a way that goes deeper than Dworkin seems to recognize.

The Problem with Moral Wisdom

The objection is not merely that judges are fallible, though they are, or that the legal system selects for a particular kind of person whose moral intuitions may not represent the full range of human moral experience, though it does. The objection is more fundamental: what Dworkin calls moral wisdom may not be a thing that exists in the form his theory requires.

When we talk about moral wisdom, we are assuming that there is a kind of insight into right and wrong that some people have more of than others, and that this insight is accessible through careful reasoning, wide experience, and good judgment. Maybe that is true. But it is also possible that what we call moral wisdom is really just a more refined version of the same limited, historically conditioned, culturally shaped moral intuition that everyone has. A judge who reasons carefully about justice may be reasoning carefully within a framework whose deepest assumptions have never been examined, and cannot be examined from inside it.

We talk about right and wrong as though morality is the ultimate category, as though the question of what is just is the deepest question we can ask. But I am not sure that is true. We see right and wrong through the lens of morality because that is the lens available to us. We do not know the origins of right and wrong. We do not know whether the categories of good and evil that structure our moral reasoning are themselves the deepest reality, or whether they are the way beings like us, in the condition we are in, perceive something whose actual nature we cannot access.

I believe everything originates from God. But even that belief does not resolve the question, because I do not know how the nature of God generates the categories of good and evil. I do not know what it looks like from outside the moral framework we inhabit. And neither does Dworkin’s Hercules, no matter how wise.

What Law Actually Is

Here is what I think all three thinkers are circling without quite landing on.

Law is a signal. It is imperfect data pointing toward a moral order we can’t yet fully see.

The evidence for this is hiding in plain sight, and it is the thing that none of Hart, Fuller, or Dworkin takes seriously enough as a philosophical observation: law changes. Not just occasionally, not just at the margins, but constantly and substantially. What was legal becomes illegal. What was illegal becomes protected. What was unthinkable becomes constitutionally required. This is not just a feature of immature legal systems. It is a feature of every legal system that has ever existed, including the most sophisticated ones.

Why does law change? The standard answers are political: power shifts, interests change, constituencies demand new outcomes. All of that is true. But underneath the political story there is a philosophical one. Law changes because human moral understanding changes, and human moral understanding changes because we are in the process of discovering something we have not yet fully seen. The movement is not random. It has a direction — imperfect and contested and subject to reversal, but real. Societies that once legally sanctioned slavery came to legally prohibit it. Courts that once permitted the execution of juveniles came to recognize that this was wrong in a way the law had failed to register.

That movement implies something. If moral understanding were purely constructed, purely a matter of social agreement, there would be no reason to expect it to move in any particular direction. The fact that it does move, the fact that we experience moral progress as progress and not just as change, implies that there is something being tracked. Something real that the law is reaching toward, catching glimpses of, periodically correcting itself in light of.

This is what law is: the human function of morality. Not morality itself. Not a reliable map of moral truth. But the institutional trace of our collective attempt to grasp something that exceeds our grasp. The fact that we have law at all — that we feel the need to codify and enforce and adjudicate claims about right and wrong — is itself evidence that we believe there is something to get right. And the fact that our laws keep changing is evidence that we know we have not gotten there yet.

Hart saw law as a system of rules. Fuller saw it as a procedural commitment to governing through norms. Dworkin saw it as an interpretive practice aimed at moral coherence. Each of them is describing part of what law is. But none of them quite says the thing that I think is most important: that law is humanity in the act of reaching for something it cannot fully hold, and that the reaching itself tells us something about what is there to be reached for.

We live in uncertainty. But uncertainty, taken seriously, is not the absence of truth. It is the presence of something we have not yet found. Law is one of the places we look.