Breton light on the origins of the Old Irish f-future

Abstract

Proto-British, unlike the later British languages but like Old Irish, distinguished a subjunctive (*be-) from a future (*bɔ(h)-). It only did so in the verb 'to be'. Breton preserves a precious trace of this state of affairs: its present conditional was derived from the subjunctive and its past conditional was derived from the future (with other verbs, the past subjunctive was derived from the preterite).