|'Must' as deduction and obligation|
Libor from the Czech Republic asks:
'The blaze......had to have been very strong? and said that was incorrect as it should have been must have been' instead. However, all the Americans I know told me this construction sounded perfectly natural to them.
It is the case that the grammar of American English at times is slightly different from the grammar of British English, but where there are differences, most grammar reference books point out any alternative versions. For example, they might list examples of some of the past tense differences as follows:
However, I have checked with all the grammar reference books that I have to hand and in none of them is had to have been listed as an alternative to must have been. It may have been used for emphasis.
had to indicates the past tense form of must when
must = obligation. Study the following:
that if we use won't/don't/didn't have to as the negative of
must, then we are expressing the absence of obligation or necessity
and in this respect it is similar in use to needn't or don't/didn't
need to. Compare the following:
must as deduction
usage of must is quite different. As in the Time article,
we are registering that we are not absolutely sure about something,
but are guessing or assuming that it has happened, will happen or
is the case. In this sense, must have is the past tense form of
must. Study the following:
Note that the negative of must be or must have is can't be or can't/couldn't have been.
again, we are making an assumption about something. Study the following: