Law is the set of customs, practices, and rules that people agree to follow. Its four main purposes are to establish standards, maintain order, redress disputes, and protect liberties and rights. Different types of law cover particular issues. For example, immigration law covers the rights of people to live and work in a nation-state that is not their own and to acquire or lose citizenship; family law concerns marriage and divorce proceedings; and property law deals with ownership of assets. Other laws deal with specific activities such as air and sea travel, commercial transactions, trusts, and biosciences.
A person who practices law is called a lawyer. Some lawyers specialize in a particular type of law, and many have graduate degrees in their field. They may also have an undergraduate degree in a subject such as philosophy or history, and they often take continuing education courses to keep up with developments in their fields. Law schools usually offer courses in ethics and jurisprudence, which are the study of how a lawyer should behave and how a court should decide cases.
A legal system may differ from one country to another, but all laws have certain common elements. They have a source in the common consciousness (Volkgeist) of the people, and they are enforced by a sovereign authority.
Laws may also have a rationale that is based on utility, the principle that an activity should be done because it has some good consequence. The utilitarian theory of law was developed by Jeremy Bentham in the 18th century. Others, including Jean-Jacques Rousseau and Thomas Aquinas, argued for a natural law that reflects unchanging moral principles that exist in nature.
In countries that have a strong tradition of respecting precedent, judges are able to find a “safety margin” of ambiguity by looking at previous decisions that have been made on similar issues. This makes consistency and prediction easier, and it reduces the time and money spent on litigation.
However, in jurisdictions that do not have a strong tradition of following precedent, fine points of law are often determined anew each time they arise. This makes the law less predictable, and it leads to longer trials and more spending on legal fees. This kind of law is known as case law. It is often necessary to combine law from multiple sources, such as statutes and case law, in order to understand an area of the law thoroughly. This is referred to as a hybrid system. Laws that are created by legislatures or agencies are called statutory law. Laws that are created by courts are called common law. The interaction of these systems is complicated. For example, an appellate court’s decision on a matter is binding only within its jurisdiction, while decisions of lower courts are not binding and only provide non-binding persuasive authority. This gives rise to a substantial amount of overlapping law.