Legal history covers the developments of laws and progress of the theory of law in various parts of the world. There are several broad traditions which constitute the major threads in the history of law - viz. the history of Roman law (jus), of Islamic law (sharia), and of Chinese law (fǎ or 法). Each has its peculiar origins but all of them involve the institutions of a society trying to regulate the possible relationships between its members. In studying these traditions, it is important not to focus on modern terminology and to apply traditional terms, in the relevant language, to describe their primary concepts.
For Roman society, laws have always been intimately connected to the rights and duties of citizens (cives). That which is binding between citizens is known as a jus (p. jura), an obligation or duty of one citizen to another. When one citizen legitimately (de jure) deserves something from another citizen, the legitimate expectation of that treatment is the first one's right. Other languages distinguish between a law that binds one citizen to another and a right that one citizen has for something from another but Latin does not, partially conflating the concepts of laws and rights. More precisely, the spirit of a law is conflated with a right, in the sense that a lex (p. leges) is a statement (written or unwritten) expressing the rights of citizens and expressing the laws that are binding between citizens (jura) regardless of what lawmakers recognizes as binding (leges). The idea that there are laws (jura) that are independent of the recognition or statement of those laws (leges) is a core notion in Roman law. When a magistrate or the Senate exercises its legislative powers, they are regarded as recognizing that, in their expertise, these legislated statements are the rights that citizens have in virtue of their citizenship - i.e. of their participation in the Roman state.
Similarly, the potestas (p. potestates) of a citizen is regarded as a right of command over other citizens. The highest form of such rights is imperium - the right of independent command within an assigned jurisdiction. A citizen with potestas that is not imperium is one who cannot exercise that power for purposes that he deems appropriate, only for given purposes from citizens with imperium. This distinction between potestas and imperium evolved from the earlier recognition of the potestas of praetors and consuls as of a higher form than the potestas of other magistrates, military officers, or private citizens. No one citizen has unrestricted imperium, which is to say that no single person in the Roman state is truly sovereign - even the emperor has limits to his rights.
On the whole, Roman jurisprudence revolves around the notion that a state is the product of people binding themselves to one another, restricting their own freedoms to do as they wish for the purposes of pax (peace) and concordia (harmony). The Roman state is seen as sufficiently well-bound that its citizens can also pursue the secondary goal of eudaimonia (flourishing); however, the other two goals are regarded as of fundamental importance to the state and its governing bodies.