 Moreover, in a sufficiency statement, Linnebo doesn’t require that the relation \(R\) be an equivalence relation; he requires only that \(R\) be symmetric and transitive. It need not be reflexive, for the domain might contain entities \(x\) such that \(\neg Rxx\) (e.g., in the case of the sufficiency statement for directions, not every object \(x\) in the domain is such that \(x\) is parallel with \(x\)—being parallel is restricted to lines). Linnebo calls such symmetric and transitive relations unity relations. When a sufficiency statement—\(Rab \Rightarrow f(a) \! =\! f(b)\)—holds, then new objects are identified. The new objects are specified in terms of the less problematic entities related by \(R\); for example, directions become specified by lines that are parallel. According to Linnebo, the parallel lines become specifications of the new objects. A unity relation \(R\) is therefore the starting point for developing a sufficient (but not necessary and sufficient) condition for reference.