3.6 Grammar. Modal verbs for certainty and possibility.

What are the modal verbs for certainty? (Positive and negative.) If you are completely sure of something you’d say must. For example, ‘He’s wearing a kilt and drinking whisky. He must be Scottish.’ What is the opposite of this sentence? Think about it. If you answer ‘He mustn’t be Scottish’, you are wrong. You are getting confused with the modal verbs for obligation and prohibition. The correct answer is can’t. ‘He’s tall, good looking and speaks three languages, he can’t be Scottish. He must be Dutch.’

What are the modal verbs for possibility?  There are three possibilities. Could, may or might. In the context of possibility, there is no difference in meaning between these three. ‘He’s got ginger hair and scruffy clothes. He may be English, he could be Welsh, or he might even be Scottish. I’m not sure.’ Many students overuse phrases like, ‘It is possible that he is ...’ This is not really necessary when there is one single word that expresses the same idea. ‘He might be...’