Legal Reasoning & Writing: From a Rule and Some Facts to an Answer

A park has a sign: No vehicles in the park. A man pushes his bicycle along the path. A child drives a battery-powered toy car. An ambulance cuts across the lawn to reach someone who has collapsed. A town has mounted an old army truck on a plinth as a war memorial. Which of these break the rule?

Most people answer fast, and most answers differ. That gap, between a rule everyone understands and a case nobody is sure about, is where legal reasoning lives. A lawyer does not guess. She asks what the rule is for, what its words ordinarily mean, what its authors had in mind, and what courts have done with similar things. Then she writes it up so that a stranger can check every step.

This piece describes how that works across the main traditions. It is about method, not about any country's current law, and it is not legal advice; laws differ by country and change.

The legal syllogism: a rule, some facts, a conclusion

The oldest picture of legal reasoning is a syllogism. The major premise is a rule ("whoever, by fault, causes damage to another must repair it"). The minor premise is a finding about the facts ("Ben, by negligence, caused Chen's broken wrist"). The conclusion follows ("Ben must repair it"). Continental lawyers call this subsumption: placing the facts under the rule. Common-law lawyers do the same thing but find the rule in cases.

Real law is rarely that tidy, because both premises are contested. Is the rule really what you say? Did the facts really happen that way, and do they fit the words? Most of a lawyer's work is on the premises, not the logic. A good way to see this is to break the rule into elements: the conditions that must all be present for the consequence to follow. Miss one and the rule does not apply.

The French text is one sentence. In the author's own English translation: any act of a person that causes damage to another obliges the person by whose fault it occurred to repair it. This is article 1240 of the Code civil; until the 2016 reform it was article 1382, so older books and judgments cite the old number. Four elements hide inside the sentence: an act, damage, fault and a causal link ("that causes"). The German code takes the opposite approach. Section 823(1) of the BGB lists the protected interests (life, body, health, freedom, property and "another right"), and requires wrongfulness and fault. Notice what the list leaves out: a pure financial loss is not on it. That is a rule you learn only by reading the article closely, which is the skill.

Reading a code article therefore means three things. Find the facts that trigger it (the elements). Find the consequence (repair, nullity, a penalty). And check its neighbours: the exceptions, the definitions elsewhere in the code, and the heading under which it sits, because where an article is placed tells you what family of rule it belongs to.

Reading a case: facts, issue, holding, reasoning

A judgment is not a story and not a rule. It is a decision with its reasons attached, and a student's first job is to take it apart. Common-law casebooks teach five parts: the facts (what happened and how the case got to court), the issue (the legal question), the holding (the answer needed to decide this case), the reasoning (why), and obiter dicta, remarks "by the way" that were not needed for the result. The holding with its reasoning is the ratio decidendi, the part later courts treat as binding. Obiter may be persuasive but it is not the rule.

Civil-law judgments have their own anatomy. A Spanish judgment is divided into antecedentes de hecho (facts and procedure), fundamentos de derecho (the legal grounds) and the fallo (the ruling). A German judgment separates the Tatbestand (the facts) from the Entscheidungsgründe (the reasons). French supreme-court judgments have been famously terse, traditionally one long sentence of reasoning, and the court has been moving toward fuller explanations in recent years. French students summarise a ruling on a fiche d'arrêt: facts, procedure, the parties' claims, the problème de droit and the court's solution. The labels differ; the work is the same.

Interpretation: what the words mean when the words run out

Words never apply themselves. The philosopher H. L. A. Hart, in a 1958 article in the Harvard Law Review, used a "no vehicles in the park" rule to make the point: some cases fall in the clear core (a car) and others in a penumbra of doubt (a bicycle, a toy car). Lon Fuller replied in the same journal that you cannot decide the penumbra without asking what the rule is for, and offered the example of a truck mounted on a pedestal as a war memorial. The disagreement is still live: how far does a judge go beyond the dictionary?

Over two centuries lawyers have named the main tools. Friedrich Carl von Savigny, writing in 1840, described four "elements" of interpretation: the grammatical, logical, historical and systematic. Spain's Civil Code puts them in a single sentence. Article 3.1 says (in the author's translation) that rules are to be interpreted according to the proper meaning of their words, in relation to their context, their historical and legislative background and the social reality of the time they are applied, attending fundamentally to their spirit and purpose. US debates use different names: textualists stress the ordinary meaning of the text, purposivists the problem the law was meant to solve, intentionalists what the drafters wanted, and some constitutional scholars argue for reading broad provisions in light of changing circumstances.

When the three readings agree you are in the core, and there is not much to argue. When they split you are in the penumbra, and the argument is the job. Note that none of the methods is "the" correct one. A judge's choice among them is itself something a good lawyer expects to defend.

Analogy: the same facts in two traditions

When no rule fits exactly, lawyers reason by analogy: this case is like that one in the ways that matter, so it should be decided alike. In common-law reasoning the "that one" is an earlier decision, and the argument is about which facts were essential. A judge can also distinguish an earlier case by showing that a fact that mattered is missing here. Edward Levi's classic An Introduction to Legal Reasoning (1949) describes this as reasoning from case to case.

In the civil-law tradition the analogy is to a provision. Spain's Civil Code, article 4.1, says (author's translation) that analogy applies when a rule does not cover a specific situation but governs a similar one in which there is "identity of reason". Same logic, different anchor.

Watch the two traditions handle the same facts. A famous common-law case, Donoghue v Stevenson [1932] AC 562, was decided by the House of Lords on 26 May 1932 by three votes to two. A woman drank ginger beer from an opaque bottle bought by a friend and, she said, found a decomposed snail in it. She had no contract with the manufacturer. Step through how each kind of lawyer would approach a modern version.

IRAC and its cousins: writing the argument down

American law students learn a formula for answering an exam question or a memo: IRAC, for Issue, Rule, Application, Conclusion. State the question; state the governing rule, with its source; apply the rule to the facts, taking each element in turn and noticing the weak points; conclude. Variants exist (CREAC puts the conclusion first and last), and practitioners usually put the bottom line up front, because a busy reader wants the answer before the proof.

Germany's equivalent is the Gutachtenstil ("opinion style"), the only way a state-exam case is acceptable. It has four moves: the Obersatz (a question put in the conditional: "A could claim damages under section 823(1)"), the Definition of each element, the Subsumtion (fitting the facts to the definition), and the Ergebnis (the result, now in the indicative). The conclusion comes last on purpose: it shows the reader that nothing was assumed. In judgments the order reverses (Urteilsstil: result first). French students write a plan en deux parties, two main parts each with two sub-parts, and in the commentaire d'arrêt they identify the legal problem before the solution. Spanish and Latin American students facing a caso práctico write the facts, the applicable articles and doctrine, and the conclusion.

Writing: bottom line first, plain words

Legal writing has a reputation for Latin and long sentences, and for generations lawyers defended both as precision. The plain-language movement, in the US, the UK and elsewhere, argues the opposite: a sentence a client cannot follow does not make the law clearer, and ambiguity usually hides in the long ones. Bryan Garner's Legal Writing in Plain English is the standard American primer. The habits are simple: say the answer first; one point per paragraph; define a term once and keep it fixed; cite the source for each rule; and put the facts that hurt your side in plainly, because the other side will.

What the traditions share is checkability. A good legal text lets a hostile reader see every step: this is the rule and here is where it comes from; these are the facts and here is the evidence; this is how I get from one to the other. That is the nearest thing law has to a proof.

What a graduate just sees

• Every legal answer is a rule plus facts. Most arguments are about one of the two premises, rarely the logic.
• A rule is a list of elements. If one is missing, the rule does not bite, so the first question is "which element is in doubt?".
• A case has a holding and everything else. Only the holding, with its reasons, is the part that binds.
• A word has a core and a penumbra. In the penumbra, arguments about purpose, history and text compete, and none wins automatically.
• Analogy is the universal tool: decide the new case like the old one if the important facts match. The dispute is always about which facts are important.
• Different traditions write the same reasoning in different orders, but they all require the reader to see the rule, the facts and the steps between.
• Plain words and the answer first are not a lack of rigour. They make rigour visible.

Where it shows up next

• Contracts & Obligations (35/04): offer, acceptance and cause are elements; most contract disputes are about whether one is present.
• Criminal Law & Procedure (35/07): every crime is a list of elements plus a mental state, and the prosecution must prove each.
• Constitutional Law (35/03): the hardest interpretation fights, because the texts are short and broad.
• Civil Procedure & Evidence (35/08): how the "facts" premise gets established.
• In the world: every legal memo, every judgment you read in the news, every terms-and-conditions clause you wonder about.

If you want to go deeper

• 📘 Textbook. Edward H. Levi, An Introduction to Legal Reasoning (University of Chicago Press, 1949). Short and still assigned; the classic account of reasoning by example.
• 📘 Textbook. Glanville Williams, Learning the Law (Sweet & Maxwell; use the latest edition). Written for English first-year students; a plain guide to cases, statutes and essays.
• 📘 Gentler. Karl Llewellyn, The Bramble Bush (1930; reissued by Oxford University Press). Lectures to first-year law students on what courts do.
• 📘 Writing. Bryan A. Garner, Legal Writing in Plain English (University of Chicago Press, 2nd edition).
• 🌐 Free course. MIT OpenCourseWare 24.235J Philosophy of Law (Spring 2012), including the Hart and Fuller debate; and 17.245 Constitutional Law (Spring 2013) for real cases to practise on.