Jurisprudence
Why it Matters
Call a law “unfair,” and whether you meant to or not, you have carried moral philosophy into a legal argument. Jurisprudence names the positions in that argument, and this activity works three of them: natural law, legal positivism, and legal realism. Your text is Lon Fuller’s The Case of the Speluncean Explorers. Five judges read one murder statute against one set of facts and still cannot agree, because they hold different views of what law is and where its authority comes from. Once you can hear those views, you can name the theory under any legal argument and build your own on purpose.
Current Context
On June 30, 2026, the Supreme Court held in Trump v. Barbara that the Fourteenth Amendment’s Citizenship Clause guarantees citizenship to nearly all children born on U.S. soil (opens in a new tab). Executive Order 14160 could not narrow that guarantee, yet the justices split 6-3 on the order and 5-4 on the constitutional question, in six opinions running 194 pages (opens in a new tab). Chief Justice Roberts traced the rule through English common law and early American practice, and Justice Alito answered that the majority had misread the original meaning of the Citizenship Clause (opens in a new tab). Justice Thomas argued that much of the governing 1898 precedent was dicta, not binding law. Nine justices read one clause against one set of facts and still divided over what the clause means, much as Fuller’s five judges divide over one statute.
Key Concepts
Jurisprudence
The study of what law is, where its authority comes from, and how it relates to morality and justice. It runs beneath every doctrinal debate: argue over how to read a statute or a constitutional clause, and you are making jurisprudential moves, usually without naming them. This activity works three schools that answer those questions differently: natural law, legal positivism, and legal realism.
Natural Law
Law draws its authority from universal moral principles that reason can discover, and human enactment alone cannot supply it. So an unjust law is not merely a bad law; on this view, it is not truly law at all. Thomas Aquinas gave the tradition its most systematic form, and Martin Luther King Jr.’s Letter from Birmingham Jail is its most forceful modern application.
Legal Positivism
A law is valid because a legitimate authority enacted it through proper procedures, and its validity does not turn on any moral judgment about its content. Many positivists add that a judge should apply the law as written: the alternative, they argue, lets judges swap the law’s clear commands for their own moral preferences. Positivism is the dominant framework in most modern legal systems, and the one natural law challenges most directly.
Legal Realism
Law is less a formal system of rules than a forecast of what courts will actually do, shaped by social, economic, and personal factors. On this view, the rule on paper counts for less than the judge who applies it and the facts before the court. Oliver Wendell Holmes Jr.’s “bad man” thought experiment is the most memorable statement of the idea, and Holmes drew a practical lesson from it: judges should weigh a ruling’s social consequences openly.
The “Bad Man” Theory
Holmes’s thought experiment in The Path of the Law: to see what the law actually is, take the view of a purely self-interested person who cares only about consequences. The bad man ignores duty and morality and wants to know only what the courts will do to him. The frame strips out moral language and defines law in strictly predictive, empirical terms.
Civil Disobedience
Breaking a law you regard as unjust, openly and on purpose, as a moral protest that appeals to a higher principle, and accepting the penalty without resistance. King’s Letter from Birmingham Jail makes its most rigorous modern case: a person has a moral responsibility, not merely a right, to refuse an unjust law. In this activity it is the hinge between legal theory and moral obligation.
Resources
- Fuller, Lon L. “The Case of the Speluncean Explorers.” Harvard Law Review 112.8 (1999): 1851–1875, through the Daytona State College Library (opens in a new tab) (The primary text for this activity; its five judicial opinions carry the schools of legal philosophy you map in Part 1 and argue from in Part 3. Sign in with your college account, then choose Get PDF. If that PDF doesn’t work with your screen reader, ask your instructor for an accessible copy with a heading for each opinion.)
- Martin Luther King, Jr., “Letter from Birmingham Jail” (1963) (opens in a new tab) (The primary source for natural law and civil disobedience; draw on it directly when you build and defend your judicial opinion in Part 3.)
- Thomas Aquinas, Summa Theologica, I-II, Q.90–114 (Treatise on Law & Grace) (opens in a new tab) (The primary source for the systematic natural law argument; Aquinas’s definitions of eternal, natural, and human law ground the natural law position in Fuller’s case.)
- The Path of the Law: Oliver Wendell Holmes, Jr. (1897), Project Gutenberg (opens in a new tab) (The primary source for legal realism and the “bad man” theory; Holmes’s case for separating law from morality is the sharpest counterpoint to Aquinas and King in this activity.)
- Frédéric Bastiat, The Law (1850) (opens in a new tab) (The primary source for the natural rights argument; Bastiat’s line between legitimate and perverted law ties into the natural law framework you apply in Part 3.)
- William Blackstone, Commentaries on the Laws of England, vol. 1, Introduction, § 2 “On the Nature of Laws in General” (1765) (opens in a new tab) (A primary source on the nature of law itself. Blackstone defines municipal law as the command of the supreme power but rests its authority on a higher natural law. Fuller’s positivist and natural-law judges each take one side of that tension.)
- YouTube: Frédéric Bastiat, The Law (1850) (opens in a new tab) (A narrated video of Bastiat’s The Law for students who would rather listen; it covers the same account of legitimate and perverted law as the PDF.)
What to Do
This activity trains you to name the theory of law under an argument, and then to argue from one yourself. Fuller’s The Case of the Speluncean Explorers, one of the most famous exercises in legal education, gives five fictional judges one murder statute and one set of facts. Two vote to affirm the convictions, two vote to reverse, and one withdraws from the case. The statute does not divide them; their theories of law do. You will map those theories, trace them to the primary texts, and write as one of the judges.
Part 1: Read and Map the Philosophies
Start with Fuller’s The Case of the Speluncean Explorers. Read each opinion for the reasoning behind its verdict. Watch what each judge treats as the source of law’s authority: the text of the statute, natural justice, or the practical consequences of the ruling. Then use the Philosophy Mapper prompt to connect the judges’ arguments to the three schools. Its table is only a starting point, so check each row against Fuller’s text before you rely on it.
Part 2: Connect to the Primary Sources
Trace each framework back to its sources in Resources. The natural law judge echoes King’s line between just and unjust laws and Aquinas’s claim that human law draws its force from natural law. The positivist judge applies the statute strictly, holding that validity comes from enactment, not moral content. The realist judge asks what outcome a sensible person in the real world could accept, the practical approach Holmes defends in The Path of the Law. Before you open a source cold, run the Primary Source Navigator prompt for its author, its central argument, and the passage that bears on the cave. Then, before you draft, use the Opinion Architect prompt to work out how specific arguments in those texts support the position you plan to take.
Part 3: Write Your Judicial Opinion
Choose the judge you most agree with, and write a judicial opinion of 400–600 words defending a decision to affirm or reverse the explorers’ convictions. Your opinion must do three things. It states your ruling and names the legal philosophy the ruling rests on. It defends that position with at least two of the primary texts from Resources. And it takes on the strongest argument against you and explains why your view still holds. Before you finalize, run your draft through the Counterargument Generator prompt. Treat its critique as real pushback: revise where an objection holds, and distinguish it where it does not.
Part 4: Share Chat Link
Include one AI chat link with a 1–2 sentence explanation of what the conversation shows and why you chose to share it.
Suggested AI Prompts
Use these prompts as a starting point, then adjust them to fit your goal. Strong prompting develops through trial, revision, and testing. It’s a foundational skill that grows into more advanced AI work such as context engineering and agent-based workflows.
Philosophy Mapper
You are a jurisprudence professor analyzing The Case of the Speluncean Explorers by Lon L. Fuller (1949). Produce a table for all five judges (Truepenny, Foster, Tatting, Keen, and Handy) with three columns: Judge Name; Legal Philosophy (Natural Law / Legal Positivism / Legal Realism / Other, with specification); and Key Reasoning (two sentences on the main argument each judge uses to reach his conclusion). After the table, identify the two judges most directly in conflict and explain in three sentences what their disagreement reveals about the fundamental divide between natural law and legal positivism. Base your analysis on Fuller’s text as written; do not import interpretations from secondary sources.
This prompt combines role assignment, structured output, and a source-grounding constraint, and the table makes the model rule on all five judges instead of lingering on the most interesting one. The closing question about the two judges most in conflict moves you from description to analysis. In Part 2, ask the AI to tie each judge’s reasoning to a passage in a primary text, and you have chained two steps, the basic move behind larger AI workflows.
Opinion Architect
I am writing a judicial opinion in The Case of the Speluncean Explorers, siding with [name the judge] and his position that the explorers’ convictions should be [affirmed / reversed]. Walk me through building my argument step by step. First, state the central legal principle my chosen judge relies on and explain in plain terms what it means. Second, identify the single strongest argument from [choose: MLK’s Letter from Birmingham Jail / Holmes’s The Path of the Law / Bastiat’s The Law / Aquinas’s Summa Theologica, Q.90–114 / William Blackstone, Commentaries on the Laws of England, vol. 1, Introduction, § 2 “On the Nature of Laws in General”] that supports that principle. Describe the argument without quoting at length. Third, identify the strongest opposing argument I will need to address and suggest how my judge would respond to it. After completing all three steps, ask me one clarifying question about my position before we continue.
Step-by-step decomposition splits a hard writing task into parts you can check one at a time. The closing question is Socratic elicitation: a model that gathers information before it writes gives better-fitted help than one guessing from a thin request. The bracket in the second step makes you pick the primary source, because that choice is your intellectual work, not the AI’s.
Counterargument Generator
I have drafted a judicial opinion in The Case of the Speluncean Explorers that argues [briefly state your ruling and the main reason]. Act as the judge in the case who most strongly disagrees with my position. Identify my weakest logical point, the specific primary text I am using in a way that could be questioned, and the one factual or legal consideration I appear to be ignoring. Be direct. I do not want a balanced assessment; I want the best possible case against my argument so I can strengthen it before I submit. Here is my draft: [paste your opinion here].
Casting the AI as the judge who most disagrees with you is red-teaming, and it works against the model’s tendency to approve what it reads. Sort the objections it raises: the ones you cannot answer quickly mark the paragraphs to rewrite before you submit.
Primary Source Navigator
I am about to read [choose one: Thomas Aquinas’s Summa Theologica, Q.90–114 / Oliver Wendell Holmes’s “The Path of the Law” / Frédéric Bastiat’s The Law / Martin Luther King Jr.’s “Letter from Birmingham Jail” / William Blackstone, Commentaries on the Laws of England, vol. 1, Introduction, § 2 “On the Nature of Laws in General”]. Give me a brief orientation in four parts: (1) who the author was and the historical moment that shaped this text, (2) the central argument I should watch for as I read, (3) the one section or passage most directly relevant to the debate in The Case of the Speluncean Explorers, and (4) one question I should hold in mind while reading to connect this text to Fuller’s case. After I read, I will return and tell you what I found. At that point, check my reading against what the text actually says and flag anything I may have overstated or missed.
Change the bracket and this prompt becomes a reusable template for all five primary texts. The closing instruction builds verification into the workflow, which matters because AI tools often paraphrase philosophy with confidence and bend the argument along the way. Read the text and form your own interpretation first, so the AI checks your reading instead of replacing it.