Past Modals of Deduction
In the same way that we use modal verbs to say how certain we are about things in the present we can also use them to speculate about the past. Have + past participle (‘have done’, ‘have been’ have stolen’ etc.) is called the perfect infinitive. When we use modal verbs to talk about the present they are followed by an infinitive without ‘to’. When we use modal verbs to talk about the past they are followed by a perfect infinitive. must + perfect infinitive We use must + perfect infinitive when we feel sure about something in the past. You must have been delighted when you heard you’d won the lottery. The thieves must have come in through the window. Look – it’s still open. Oh no! Where’s my car? Someone must have stolen it! might/may/could + perfect infinitive We use might , may or could with the perfect infinitive to say that we think something was possible but we aren’t sure. The thieves might h...