The clan (_gens_) was an aggregate of individuals supposed to be sprung from a common source, a social union, with common rights in private law, which had as its theoretical basis the notion of descent from a single ancestor. According to the juristic theory of the clan, all its individual members would, if their descent could be traced through every degree, have sprung from two individuals who were within the power of this ultimate ancestor, a sign of this original _potestas_ being the common gentile name.[32] The members of a clan are to one another either _agnati_ or _gentiles_. In many cases the difference of nomenclature was based merely on the degree of certainty in the relationship. They were _agnati_ when the common descent could be traced through all its stages; they were _gentiles_ when the common descent was only an imagined fact, based on the possession of a common name. As a rule _agnati_ are also _gentiles_; but there might be groups of agnates who could never be _gentiles_—groups, that is, of proved relationship through the male line, who could not, for reasons which we shall soon specify, form a _gens_. If we believe that the Roman Patriciate represented those who alone possessed the legal status of heads of families (_patres_)[33]—since, the _familia_ being the unit of the clan, the rights of a clan-member (_gentilis_) imply the position of a _paterfamilias_—it follows that the Roman _gentes_ were, as they are represented by tradition, originally exclusively patrician, and that the terms _gentilis_, _gentilitas_ implied a perfect equality of status among the only true members of the state. The words became restricted to a certain section of the community in consequence of the evolution of plebeian rights, i.e. in consequence of the Plebeians becoming in strict law _patres familias_. The logical consequence of this should have been, where groups of such families bore a common name and were believed to have a common descent, that these groups should form _gentes_. But history is illogical, and this conclusion was not reached.