In Grammar 6-1, you looked at modal verbs of probability in the present. In this lesson, you are going to learn about modal verbs of probability in the past.
Usually, when people talk about the past, they know what is true or what happened, so they use past tenses.
- Most of the Egyptian pyramids were built as tombs for the country's pharaohs.
However, sometimes we don’t know exactly what happened, but we still want to guess, speculate, or make conclusions based on the evidence we have or what we know is logical or possible. In English, different modal verbs are used with have and the past participle of the main verb to express how certain someone is when speculating about the past.
Expressing Certainty
When you are almost certain that something was true about the past, you can express this using must + have + past participle for positive statements. Usually, people are so certain because they have evidence or because there is no other possible or more logical explanation.
- It must have taken the ancient Egyptians a long time to build each pyramid. (They are massive structures.)
- They must have had knowledge of astronomy. (The Great Pyramid’s four corners are aligned north, south, east, and west.)
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