Since Justice Holmes asserted that “the life of law is not logical, but experience,” lawyers and judges in the United States have downplayed the importance of formal logic in understanding law and legal thought. Many jurists and practitioners feared that recognizing that logic is at the heart of law risked returning to the rationalist excesses of formalist jurisprudence that dominated nineteenth-century legal thought. It is, after all, against this formalist tradition that Holmes wrote. And it was in stark opposition to this tradition that members of the realist legal movement in America, as well as the free rights movement in Europe, directed much of their energies in the early twentieth century. There are good reasons to remain skeptical of overly rationalistic representations of law and judicial practice. The web of historical doctrine, legal principles, and factual nuances that underlies every judicial decision is far too complicated to permit critical evaluation using a single method of evaluation, including the principles of logic. We are therefore rightly concerned when we recall the formalist visions of nineteenth-century jurists – visions that found the essence of jurisprudence in the logical derivation of conclusions necessarily required by predetermined legal principles. Understanding essentially means drawing conclusions from an already accepted logical system. While it is true that many other factors – from self-interest to moral values, from psychology to science – fuel the decision-making of lawyers and judges, all of these factors carry the pervasive dye of reason and logic. Litigants may rely on the psychology or feelings of the jury, but only to the extent that they reasonably expect to influence the jury to draw rational conclusions in favour of their client. Personal interest may be the sole driving motive of each party in drafting a contract, but the rational recognition that insisting on onerous provisions is likely to undermine the entire contractual agreement tends to keep everyone`s self-interest at bay. And although judicial practice requires a high degree of “value judgment” in the selection, interpretation and application of legal principles, these value judgments are not exempt from the constraints of reason.

As one appeals court noted, “All legal analysis should begin at the point of reason, follow a logical path, and arrive at a fundamentally fair result.” (Sunrise Lumber v. Johnson, appointment No. 165). To criticize, annul or annul an administrative or judicial decision as “arbitrary”, “capricious”, “not supported by the law” or “contrary to jurisprudence” means to say no more, no less, that the decision lacks logic and reason. Essentially, the field of law, and perhaps especially the practice of judicial decision-making, are exercises in practical thinking. There is certainly more to law than logic. However, the myriad of factors that contribute to good legal practice and fair judgment suggest that the “life of the law,” while not just logical, is a variety of activities, all of which use and depend on reason in specialized ways. The level of detail required when drafting contracts, wills, trusts and other legal documents is rational precision; The care that litigators must take in planning and strategy in deciding how to present their case is rational diligence; The written and oral reasoning required for the practice of appeal is obviously a rational ability; the talent expected of administrative judges to produce consistent findings of fact and legal conclusions is a rational talent; And the ability of trial and appellate judges to impartially and impartially separate the core reasoning from rhetorical and emotional chaff from adversarial representation in order to render legally justified judgments is a rational skill. The above is an excerpt from Professor Douglas Lind`s book Logic and Legal Reasoning (2nd edition, The National Judicial College Press, 2007). Lind, who is a professor in the philosophy department at the University of Idaho in Moscow and a lawyer, teaches the logic portion of the NJC`s logic and opinion writing course.

The logic part of the course is a two-day immersion in logic, where participants learn a foundation in deductive and inductive logic and have the opportunity to discuss the use of logic in legal reasoning. It is therefore interesting for law practitioners and students to have an understanding of the basic principles of logic that are regularly used in legal reasoning and judicial decision-making. This understanding requires, to a large extent, the ability to navigate the processes of inductive reasoning – the methods of analogy and inductive generalization – by which conclusions are drawn based on past experience and empirical observations. The common law approach to developing jurisprudence, as well as the general rule often referred to as the “rule of law” – that similar cases are decided immediately – are logically based on inductive reasoning. But somewhere between strict formalist jurisprudence and utter disregard for logic and argumentative form, law and judicial practice truly find peace. Although all that is usually repeated by Justice Holmes is the concise remark quoted above, his jurisprudential writings, as well as his legal opinions, make it clear that it was never his intention to pretend that logic is not a central aspect of law or judicial decision-making. He, along with legal realists and other critics of legal formalism, have recognized that evaluation and the creation of arguments are at the heart of the lawyer`s judgment. Equally important is a second basic category of reasoning – deductive logic, especially the forms of deductive arguments known as “syllogisms.” These are the classic forms of the deductive argument, which consist of a main premise, a secondary premise, and a conclusion. It was this aspect of logic that provoked such virulent opposition to formalism a century ago. And it is this aspect of logic that has been so downplayed throughout the twentieth century. Yet even a rudimentary understanding of deductive logic gives lawyers, judges, and law students a valuable tool for determining whether an argument in a legal opinion or brief is valid or misleading.

This article discusses the legal applications of logic, with a particular focus on logic models of legal reasoning. We argue that the law is a rich testing ground and an important field of application for logic-based AI research. The initial applications of logic to the presentation of legislation are reviewed, with an emphasis on representation and the legal conclusions that emerge from this presentation as a derivation. This includes the presentation of deontic concepts, normative positions, legal ontologies, time and change. Then the legal applications of logic are reviewed, where legal rules are not only applied, but are the subject of argumentation and discourse. This includes discussing the application of legislation in unforeseen circumstances, interpreting reasoning in light of the facts of a case, and providing evidence to establish the facts of a case. This part of the review places particular emphasis on argument-based approaches. This also applies to the last part, which deals with formal models of legal procedure and multi-agent interaction in court proceedings.

The review concludes with the identification of some of the key open research questions. The review shows that modern legal applications of logic confirm the recent tendency to extend the scope of deduction logic to the flow of information, reasoning, and interaction. A woman with many firsts, Judge Bernice B. Donald vom U.S. Court of Appeals for the 6th Circu. In 1979, Congress created four additional Article III judicial positions in the United States District Court in .