legal reasoning: analogy

The Significance of Reasoning By Analogy & Precedent in Legal Argument
Compare discussions of a difficult public issue as conducted in a law school with discussions of the same issue in a business school or public policy school. Take, for example, the issue of "surrogate motherhood" (sometimes called, "contract pregnancy").(1) Should society permit and enforce agreements in which a woman promises to become pregnant using the sperm of the man proposing the contract, to carry the pregnancy to term, and to turn the baby over to the man (and usually his wife) in exchange for money? Discussions in a business school or public policy school are likely to explore the social consequences of such agreements.(2) How are they likely to affect the availability of babies for families that want them, the value of women's labor, and perhaps, the societal views of children, pregnancy, and women's bodies?(3)

These themes are bound to arise in a law school classroom, too, but so will a very different line of analysis. Law students find courts and legislatures asking questions such as: is surrogate motherhood more like baby selling, which is forbidden by law, or an employment contract, which is lawful? Is the baby more like goods that can be freely exchanged in the marketplace, or more like human tissues and organs, about which there is great controversy?(4) Is the surrogate mother who changes her mind and wants to keep the baby more like a woman who has agreed to place her expected child up for adoption -- and by law is allowed a grace period within which to change or mind -- or like a seller who agreed to provide a unique good -- and by law may be compelled to do so? These questions all draw comparisons between the surrogacy context and other contexts already settled by law. These questions, in short, pose analogies to precedents, decisions that have already been made.(5)

Treating a disputed case by reference to the settled treatment of a prior case is a familiar instance of reasoning by analogy in law, although lawyers and judges also make analogies with sources besides prior judicial opinions.(6) Legal reasoning makes use of analogies to precedents for three reasons. The first is a commitment to equality: like cases should be treated alike; unlike cases should be treated differently. The second reflects a conception of the "rule of law" as an ideal; issues should be resolved by reference to established standards rather than whim. This ideal promotes predictability for people affected by law and accountability by people who implement law. Predictability and accountability are values independent of correct or even marginally better solutions to problems. The third reason behind law's use of analogies stems from their effectiveness in producing answers to problems that can be perplexing and divisive. Reasoning by analogy can prompt a flash of insight about how to respond to a case in doubt. This is especially helpful when the analogy stems from a pre-existing, authoritative decision; being able to point to past authoritative decisions that seem similar helps to prompt and justify decision in a sea of otherwise competing considerations. Reasoning by analogy serves law's basic goal of resolving practical problems while sustaining a relatively predictable and fair system for solving problems in the future. At different times, and within different legal communities, particular analogies or analogies in general may hold more or less persuasive power or seem more or less gripping. Yet their distinctive presence in legal reasoning justifies a closer look at how lawyers and judges use analogies.