Precedents are used for many different purposes. When a statute is vague, precedents are often used to argue for one interpretation over another. When no statute applies directly, precedents are often used to argue about what the law is. Precedents can also be used in arguments for general questions of fact, or simply as sources of persuasive rhetoric.
The form of arguments from precedents also varies. Often a judge or lawyer merely quotes part of the opinion in the precedent and treats that quotation as an authoritative pronouncement of the law. Arguments from precedents are then similar to arguments from legislative statutes, and there often arises a similar need to interpret the judicial pronouncement in the precedent. In other precedents, the judge chooses to make the decision with- out explicitly formulating any general rule of law. The precedent can still be used to argue for future decisions by emphasizing analogies and discount- ing differences between the precedent and the present case.