(If anyone could please help me with plain English, I would greatly appreciate it)
I just don't understand why 'an entity typically ...' can be reason enough to support the notion of 'the vast majority can be accounted for under either view.'
Is it my limited understanding of the English used here that's hindering the uptake, or the authors' unreasonable logic? To me 'an entity ...' only explains how there is a great deal of overlap between the set of entities that are familiar to the hearer and the set of entities that are uniquely identifiable to the hearer. To me it seems this does not explain that the two theories combined cover the vast majority of uses.
Research into the meaning of the English definite article has generally been approached from one of two perspectives, characterizable as 'familiarity' and 'uniqueness.' That is, felicitous use of the definite article has been argued to require that the referent of the NP be either familiar within the discourse or uniquely identifiable to the hearer. The vast majority of uses can be accounted for under either view, since an entity typically must be familiar in a given discourse in order to be identifiable to the hearer.
*NP: noun phrase, i.e. a noun with modifiers, or just a bare noun. (This annotation is added by Sssamy)
('Uniqueness, Familiarity, and the Definite Article in English' by Betty Birner and Gregory Ward)
Any and all help would be greatly appreciated.