Philosophy of law is a branch of philosophy that examines the nature of law and law's relationship to other systems of norms, especially ethics and political philosophy. It asks questions like "What is law?", "What are the criteria for legal validity?", and "What is the relationship between law and morality?" Philosophy of law and jurisprudence are often used interchangeably, though jurisprudence sometimes encompasses forms of reasoning that fit into economics or sociology. Philosophy of law can be sub-divided into analytical jurisprudence, and normative jurisprudence. Analytical jurisprudence aims to define what law is and what it is not by identifying law's essential features. Normative jurisprudence investigates both the non-legal norms that shape law and the legal norms that are generated by law and guide human action. Analytical jurisprudence Unlike experimental jurisprudence, which investigates the content of legal concepts using the methods of social science, analytical jurisprudence seeks to provide a general account of the nature of law through the tools of conceptual analysis. The account is general in the sense of targeting universal features of law that hold at all times and places. Whereas lawyers are interested in what the law is on a specific issue in a specific jurisdiction, philosophers of law are interested in identifying the features of law shared across cultures, times, and places. Taken together, these foundational features of law offer the kind of universal definition philosophers are after. The general approach allows philosophers to ask questions about, for example, what separates law from morality, politics, or practical reason. Often, scholars in the field presume that law has a unique set of features that separate it from other phenomena, though not all share the presumption. While the field has traditionally focused on giving an account of law's nature, some scholars have begun to examine the nature of domains within law, e.g. tort law, contract law, or criminal law. These scholars focus on what makes certain domains of law distinctive and how one domain differs from another. A particularly fecund area of research has been the distinction between tort law and criminal law, which more generally bears on the difference between civil and criminal law. Several schools of thought have developed around the nature of law, the most influential of which are: Natural moral law theory, which asserts that law is inherent in nature and constitutive of morality, at least in part. On this view, while legislators can