章振邦《新编英语语法》Lecture 1718情态助动词和半助动词教学课件.ppt

Lecture 1718 Auxiliaries 17.2 Epistemic and non-epistemic use of modals In terms of the meanings they express, modals can be divided into two categories—epistemic and non-epistemic. The function of epistemic modal is to make judgements about the possibility or necessity that something is or is not the case. The non-epistemic category only describes the fact as it is, e.g.: He must be very careless. We must be careful. See P206-207 In their epistemic uses, the modals can be arranged on a scale according to the degree of certainty or uncertainty that the speaker feels. Might can be viewed as the most uncertain, while must as the most certain. Syntactic features of epistemic modals The following 5 syntactic features are common to all epistemic modals: All epistemic modals can combine with a perfective infinitive. All epistemic modals can combine with a progressive infinitive. All epistemic modals can be used in existential sentences. All epistemic modals can combine with stative verbs. All epistemic modals can be used with an inanimate subject. 17.1 Modals and modal meanings ★ ability and possibility may not May not in written form may mean very different things: “impossibility” or “prohibition”. In the sense of “impossibility”, stress normally falls on may; in denoting “prohibition”, stress falls on not. Thus in written language, can’t is often preferable to may not in the sense of “impossibility”. He may not go tomorrow. = It is possible that he will not go tomorrow. He may not go tomorrow. = I don’t permit him to go tomorrow. can may Note the difference between the “possibility” expressed by can and that by may. In positive statements, can usually expresses “theoretical possibility”, while may expresses “factual possibility”. Mr Reed is in poor health. He can be ill at any time. Mr Reed looks pale. He may be ill. P194 ★ permission and prohibition may not Note that the past form of may not ( in the sense of