In Early Irish society the tuath (plural tuatha; people, tribe; country, territory; the state, as opposed to the church) was the basic territorial unit to which every individual belonged. It could also refer to the laity residing there. It is usually translated as "petty kingdom" or "tribe," although neither is a completely accurate translation. The tuath was a small political unit— much smaller than the contemporary kingdoms of Mercia or Kent in England. It has been variously estimated that there were as many as one hundred tuatha in Ireland between the fifth and twelfth centuries. Provinces were made up of several such tuatha, each with its own king. With an estimated population in Ireland of roughly 500,000, an average tuath would have had around five thousand members. Despite the fact that the tuath was a rather small unit, it was the center of almost all social, political, and religious interaction for its members.
The boundaries of a tuath were often defined by bog, woodland, or mountains, but it would usually also have had an area of well-cultivated land, that is a mag (plain), contained within it. Some tuatha were named after the mag, for example, Mag Cerai from the territory of the Fir Cherai. Each tuath had its own sacred site where its kings were inaugurated. Such sites were often signified by a sacred flagstone (lecc) or sometimes by a sacred tree (bile). To remove or destroy these was one of the most grave violations that could befall a tuath.
According to the law tracts a tuath must have a church, an ecclesiastical scholar, a poet, and a king. Of these, the king was perhaps the most important to the tuath. All free men of the tuath owed him loyalty, and he in turn acted as their appointed representative in all matters concerning the tuath and its neighbors. It was through the king that the tuath made cairde (pacts) with other tuatha. The king was also responsible for summoning a slogad (hosting) to defend the tuath or to launch an attack as required. The king might also become a client to another, more powerful king, thus placing the tuath in a network of tuatha led by a regional or even a provincial ruler.
Although tuath is often translated as "petty kingdom" it also refers to the people of that kingdom; thus tuath has the additional meaning of "people" or "tribe." This sense is particularly important with regard to the functioning of the Early Irish law codes. An individual had very limited rights outside his or her own tuath, and in fact to leave one’s tuath permanently was considered dishonorable. The exceptions to this were members of the church (priests, monks, abbots, and bishops who fell under the ecclesiastical laws), poets (members of the learned class), and kings, as well as a woman marrying into a family outside her own tuath. For ordinary people, leaving the boundary of the tuath could be very dangerous, unless a treaty had been agreed guaranteeing the protection of the individual while in another tuath. Without such a treaty a stranger could legally be killed, because once outside his own tuath he no longer had any eraic (honor price), thus leaving his kin-group with no means of legal redress. Thus, the Early Irish legal system, which was essentially a system of civil law, was tied to the tuath, although the laws themselves were uniform across all tuatha.
It is partly due to this system of law, as well as to the segmentation of ruling dynasties, that the tuath continued to have a place in Irish society. The tuatha enabled the great dynasties to maintain a degree of cohesion, and to stem competition for the over-kingship by allowing the heads of subordinate branches to be kings of their own tuatha. This practice helped to preserve the system of petty kingdoms into the post-Viking period.
However, the king never had executive command over the tuath. Rather, the Law worked through a system of pledges and bindings using the individual’s honor price. These pledges were administered by lawyers. In addition the tuath did not provide the king with any real tax base, nor did he have control of a standing army. Thus the tuath never evolved beyond a very simple state, and under ever-increasing pressure from the provincial kingships, the tuath eventually lost its independent status. By the eleventh and twelfth centuries tuath had come to mean a small, semiauto-nomous territory ruled by a taoiseach (leader).
