The grammaticalisation of epistemic modal verbs from earlier deontic meanings in English has been shown to be related to the operation of the second Maxim of Quantity (Q2) of Grice (1975), which holds that a restricted quantity of information is extended to refer to a wider range of meanings than are actually expressed. In the case of the English modals, the suggestion of notions of permission, ability, and volition carries the expectation that the situation predicated by the verbs expressing such meanings will in fact be realised in the future (Traugott, 1989), hence leading to future-projecting uses. Used in the past, however, the modal verbs are equally as likely to convey meanings of hypotheticality and counterfactuality, meanings which refer to the non-realisation of the modal predicates, and which could be predicted to result from the operation of the first Gricean Maxim of Quantity (Q1) (in which an unrestricted quantity of information is understood to have a restricted interpretation). The present study examines the grammaticalization of English would over an extended time period, and offers a single analysis which accounts for the evidence of both Q2 and Q1 implicatures in the development of past future, hypothetical, and counterfactual meanings. Quantitative data illustrating the emergence of such meanings are also investigated.