The article is concerned with the historical development of counterfactual (or irrealis) constructions from the earliest Old English texts until modern times. Throughout the hi story of English one can observe here an interesting interaction of mood, tense, modality and other counterfactual markers, which undergo significant cyclical changes. There have been two competing tendencies as far as verb forms are concerned. At some stages parallel verb forms prevail in both clauses of the conditional period. On the other hand, being more remote from the reality than the protasis, the apodosis tends to take a more moda! form. In Modern English (especially 18th and 19th centuries) certain changes are slowed down or even prevented due to strong authority of prescriptive grammarians
