The word ‘positivism’ was probably first used to draw attention to the idea that law is ‘positive’ or ‘posited’, as opposed to being ‘natural’ in the sense of being derived from natural law or morality.

Legal positivism is a philosophy of law that emphasizes the conventional nature of law; that it is socially constructed. According to legal positivism, law is synonymous with positive norms, that is, norms made by the legislator or considered as common law or case law. Formal criteria of law’s origin, law enforcement and legal effectiveness are all sufficient for social norms to be considered law. Legal positivism does not base law on divine commandments, reason, or human rights. As a historical matter, positivism arose in opposition to classical natural law theory, according to which there are necessary moral constraints on the content of law.

Legal positivism does not imply an ethical justification for the content of the law, nor a decision for or against the obedience to law. Positivists do not judge laws by questions of justice or humanity, but merely by the ways in which the laws have been created. This includes the view that judges make new law in deciding cases not falling clearly under a legal rule. Practicing, deciding or tolerating certain practices of law can each be considered a way of creating law

Legal positivism has been criticized by the naturalists as sterile and inadequate because it fails to consider moral considerations.

The theory conflicts with ordinary usage by denying the name ‘law’ to rules which are generally classified as legal, e.g., rules of customary law, international law and much of constitutional law. None of these rules originates from a sovereign command – customary law springs from habitual behaviour rather than from precept, international law is a system of customary rules originating from state practice, and constitutional law consists in part of conventions, which have evolved without legislation or judicial decision.

Legal moralism is the view that the law can legitimately be used to prohibit behaviors that conflict with society’s collective moral judgments even when those behaviors do not result in physical or psychological harm to others. According to this view, a person’s freedom can legitimately be restricted simply because it conflicts with society’s collective morality. Thus, legal moralism implies that it is permissible for the state to use its coercive power to enforce society’s collective morality.

Patrick Devlin argues that a shared morality is essential to the existence of a society— “If men and women try to create a society in which there is no fundamental agreement about good and evil they will fail; if, having based it on common agreement, the agreement goes, the society will disintegrate. For society is not something that is kept together physically; it is held by the invisible bonds of common thought. If the bonds were too far relaxed, the members would drift apart. A common morality is part of the bondage. The bondage is part of the price of society; and mankind, which needs society, must pay its price.”

Formalism refers to the view that judging is a rule-bound activity. According to formalists, judges apply the governing law to the facts of a case in a logical, mechanical, and deliberative way. For the formalists, the judicial system is a “giant syllogism machine,” and the judge acts like a “highly skilled mechanic.” Once lawmakers produce rules, judges apply them to the facts of a case without regard to social interests and public policy.

Formalism owes much of its existence to the notion of law as legal science. This school of thought views law as a rational, gapless, complete, and almost geometrical system. It is a self-encompassing system in a sense that all that is needed can be found within the system, within the legal rules.

Posner writes that— “Legalists decide cases by applying pre-existing rules or, in some versions of legalism, by employing allegedly distinctive modes of legal reasoning, such as ‘legal reasoning by analogy.’ They do not legislate, do not exercise discretion other than in ministerial matters (such as scheduling), and do not look outside conventional legal texts, mainly statutes, constitutional provisions, and precedents (authoritative judicial decisions), for guidance in deciding new cases. For legalists, the law is an autonomous domain of knowledge and technique.”