What is the Philosophy of Law?
An introduction to Lon Fuller's 8 principles of legality, and the application of legal philosophic frameworks to lawmaking
In the latter half of The Foundations of New York, I take students through a basic bill-drafting exercise—they must pretend they’re members of the New York City Council writing new laws. The exact structure of the exercise varies a bit from cohort to cohort, but the overall themes play out the same way.
Students come up with bills, present them to the class for consideration, and then…the wheels come off. But in a fun way.
By this point in the class, everyone knows that writing laws is not as easy as it might seem, and prior to the exercise I give them some further prompts to think about, all of which we’ve previously discussed in one form another. For example:
You’re writing a city law. How do you know that the city has the power to write that law, as opposed to the state?
How do you know that the law you’re writing doesn’t already exist?
There are different kinds of law. How do you know whether your bill, which is a form of statute, should contain all of its provisions in statute—as opposed to requiring further legal development in administrative law? What is the right balance there?
Who will enforce this law? What are the procedures and penalties involved in enforcement? Who is in charge of those (hint, it’s often OATH)?
What will this cost? Will it incur operational expenses, capital expenses, or both?
Will there be legal challenges to this law in court? What might those be? How might the law be written to survive them?
The list goes on.
You can see how draft laws easily run into a volley of questions and implementation problems. The class acts as the Loyal Opposition to point as many of those out as possible for each bill. It’s all in good fun, and a way to reinforce the idea that good legislation, and good legislators, are rarer than one would expect.
So you might be wondering: how do good laws get written? How do good legislators know all of the relevant considerations to take into account? How can I become someone who writes draft legislation?
The Foundations of New York does not cover the answers to these questions beyond a basic introduction. But if you want to learn these things, you should be heartened to know that it is learnable, that there are definite frameworks you can master, and that you can productively engage in bill drafting. If you can do this at even a basic level, the way you think about “what the law should be” will be radically altered. Why? Because you can be concrete about it.
One field you want to learn is: the Philosophy of Law, also called jurisprudence.
The Philosophy of Law
Generally speaking, legal philosophy asks “what is the law?” It then asks more detailed version of that question, like “what is good law?” It also asks how law relates to other systems of norms that we care about, like ethics, custom/tradition, markets, and more.
There are many frameworks within this field that can help you. Assuming you’ve mastered a few technical ones like the hierarchy of authorities, which ground you in the practical reality of law (where is it written, who makes it, etc), you can move on to others.
Lon Fuller’s Eight Principles of Legality
Generality: this is the most basic requirement, which means there must be rules, or rule of law. This opposite of this is rule of man, or rule via ad hoc decisions unbound by any general principles that the subjects of the law can know.
Promulgation, or publicity: the laws must be promulgated, or made available, publicly. If they aren’t, how can they reasonably function as rules? They can’t. Citizens won’t know what to do.
Retroactivity: retroactive laws cannot be passed that punish past behavior that was legal at the time. Laws can only apply forward in time (prospectively), not backward (retrospectively). Otherwise all present action, even if legal, is potentially subject to punishment in the future for illegality.
Clarity, or intelligibility: laws must be written as clearly as possible, so that they are maximally understandable to anyone who reads them.
Contradiction: laws should not contradict each other. Otherwise, how does anyone know which to obey and structure their activity around? This can also be called the attribute of “consistency.”
Compliance, or practicability: laws must be written to reasonably allow people to comply with them. For example: what if the law said you had to appear in court in response to a speeding ticket within 10 seconds of that ticket being issued, otherwise you’d incur fines and jail time? No one could comply with this.
Constancy, or stability: the law must remain stable, and must not constantly change. If it changes too often, people cannot make future plans for themselves or their businesses. They won’t know whether contracts are safe, and more.
Congruence: there must be congruence between the law as written and the law as declared and acted upon by officials.
While the list seems simple, the evaluation of a law against the list is not necessarily so. As Fuller says in The Morality of Law, paraphrasing Aristotle:
It is easy to see that laws should be clearly expressed in general rules that are prospective in effect and made known to the citizen. But to know how, under what circumstances, and in what balance these things should be achieved is no less an undertaking than being a lawgiver.2
The point of the eight criteria isn’t to say that each should be maximized at all times, just that you should pursue each as much as is relevant. For example, the military must have state secrets about weapons systems and certain elements of international diplomacy. Full detail about those things, and the rules that govern them, cannot be promulgated, because they must be balanced against security needs.
Or consider the rule against retroactivity. Article 1, Section IX, Clause 3 of the U.S. federal constitution says: “No Bill of Attainder or ex post facto Law shall be passed.”3 This is a rule against retroactivity. Does something count as ex post facto if it illegalizes an ongoing activity, versus something that was done one time in the past? Is there a difference? What about if something was a crime under one statute, but that statute is replaced with another one that criminalizes the same thing, but for a different reason—can you be retroactively convicted by the new law if your activity is discovered, even though it was technically illegal in a different way when you did it?
The eight principles of legality are not enough by themselves to evaluate a law, but they are a necessary component of the process.
The law is a difficult, technical subject that is chronically underestimated by many people. But if you get used to using different frameworks like Fuller’s principles of legality, you actually cultivate a pretty good intuition for legislation. Like anything else, practice produces mastery.
Philosophy of law is practical
Legal philosophy, in its proper form, is a fundamentally practical subject. It helps you understand the law and government, both what they are and what they could be. One of the best ways to learn the subject is to pair stories and dialectic with actual practice: write or read laws that effect you, that you can watch being made, and that you could reasonably participate in making.
This most often means examining local law, or sometimes state law. You can go to the legislative hearings where your government considers new laws—you can watch human lawmakers and see how they weigh (or not) different ideas. If you do this regularly, you can talk to staff and others who are actively invested in lawmaking and see how they think about the process. You’ll see how other frames in legal philosophy are useful, like the difference between being a legislator as a personal job versus as a wise public servant.
Even if you witness bad lawmaking, you will gain great understanding nonetheless. Being able to answer “Why are bad laws made?” is as vital as answering “How do we make good laws?” They are two sides of the same coin.
Want to learn more?
If this sounds interesting to you, I’ll be teaching an introductory seminar on legal philosophy and lawmaking in early 2024. You can sign up to be notified when signups are live.
If you want to read more about legal philosophy, I highly recommend Lon Fuller’s The Morality of Law. It is not the final word on legal philosophy by any means, and it’s embedded in a larger philosophical context, but it’s a great introduction. Get the second edition that was revised in 1969, since it has extra material that the first edition from 1964 does not have.
You can buy the book anywhere you want, but you can also borrow it for free from the Internet Archive here. The eight principles of legality are discussed in Part II: “The Morality That Makes Law Possible.”
Fuller also tells two great illustrative stories in the book that I’ll point you to:
The tale of King Rex in part II of the book: a king tries to make the laws of his land, but repeatedly fails as he encounters each of Fuller’s eight principles. Needless to say, this part of the book is called “Eight Ways to Fail to Make Law.”4
“The problem of the grudge informer” in the book’s appendix, which is eponymously entitled. In this chapter, you are asked to take on the role of a minister of justice. You’ve just taken power after deposing an unjust regime led by the Purple Shirts, who allowed all kinds of terrible things under the law. You must now decide how to deal with all past activity now that just governance has been restored. Fuller delightfully walks you through the challenges and considerations of this scenario.5
He called these the “inner morality of the law,” and each one a “desideratum of a system for subjecting human conduct to the governance of rules.” pp.46 of the 1969 revised edition.
Fuller, Lon. The Morality of Law. Second edition, published in 1969. pp. 94
Fuller here is specifically paraphrasing this quote from Aristotle’s Nichomachean Ethics, Book V, 1137a: “But how the just things are done and how they are distributed—this is indeed a greater task than to know what is conducive to health, since even here to know about honey, wine, hellebore, cauterizing, and cutting is easy, but to know how one must administer them with a view to health, and to whom and when, is as great a task as to be a physician.”
Pages 33-38 of the 1969 revised edition of the book.
Every war or regime change carries this kind of consideration with it. The Sixth Article of the Treaty of Paris that ended the American Revolution deals with it thus: “That there shall be no future Confiscations made nor any Prosecutions commenced against any Person or Persons for, or by Reason of the Part, which he or they may have taken in the present War, and that no Person shall on that Account suffer any future Loss or Damage, either in his Person, Liberty, or Property; and that those who may be in Confinement on such Charges at the Time of the Ratification of the Treaty in America shall be immediately set at Liberty, and the Prosecutions so commenced be discontinued.”