Law is a term which must be variously defined, according to its application. The laws of nature, as expounded by men of science, are general propositions as to the order in which physical events have occurred, and will probably recur; the moral law, or the law of God, is a body of truth thrown into the form of rules for the guidance of human conduct. But when we speak of law we usually mean to indicate the law which is set and enforced by civilised states. Law, in this sense, derives its sanction, or binding force, from the penalties by which men are constrained to obey it or punished for breaking it. The earliest source of law is custom; the customary rules of a primitive community formed the basis of the Civil Law at Rome, as they form the basis of the Common Law (q.v.) in England. Customary law is rigid and formal; in a progressive society it is relaxed and improved by the use of legal fictions, by the influence of Equity (q.v.), and by legislation. At Rome, for example, the growing commerce of the city compelled the prætor to go beyond the civil law (which was a law for Romans only), and to devise a new law of nations, based on principles of equity, such as all civilised men could understand. When the Romans began to study Greek they identified this law of nations with the law of nature, as expounded by the Stoics. The civil law, amended and rationalised by successive prætors and emperors, has furnished most of the nations of modern Europe with the greater part of their legal rules and ideas; even England, while refusing to borrow directly from the Corpus Juris Civilis, has derived no small part of her law from that source. Scots law has largely drawn its principles and nomenclature from Roman law.
It is usual to distinguish public law (constitutional and criminal) from private law (which applies to personal status, family relations, property, and contract). Canon Law (q.v.) is not received, as an entire system, by any modern state; but its rules are followed in defining the powers and functions of ecclesiastical persons. The Law of Nations, or International Law (q.v.), is also divided into public and private.
See such works as Maine's Ancient Law, Colquhoun's Civil Law, Austin's Jurisprudence, and Pollock and Maitland's History of English Law (1895); also the articles CODE, CONGRESS, CRIMINAL LAW, JURISPRUDENCE, JURY, JUSTINIAN, LAND LAWS, PARLIAMENT, &c.