The Law is a system of enforceable rules that regulate human behaviour. The study and exercise of the Law has existed ever since the first civilisations, and – by dealing with matters of power and morality - it is intimately connected with both Politics and Philosophy, as well as Business and Economics. An extensive field of study – known as jurisprudence – has developed to study the law and legal practice. Lawyers and legal scholars may specialise in such fields as contract law, tort law, environmental law, and criminal law. Legal jurisdictions can be classified into two, main types – civil law systems, where a single central body produces legislation, and common law systems, where the decisions made by individual judges are legally binding. Though many students who gain a Masters in a legal field go on to become lawyers, many also go into politics or commerce, as their familiarity with legal process is highly sought-after.