Deductive Reasoning and guessing with Modal Verbs must, may/might, can't/couldn't

Welcome to today's lesson on modal verbs used for deduction. In the English language, we often use modal verbs such as "must," "may," "might," "can't," and "couldn't" to make deductions or draw conclusions based on the available evidence. It is a kind of guessing exercise. Understanding how to use these modal verbs effectively is crucial for expressing certainty, probability, or impossibility in various situations. Usually, when we use these verbs, we are speaking with a thoughtful intonation, and it is important to do this in your spoken English.
1. Must:
When we use "must" for deduction, we are expressing a strong belief or certainty about something being true based on evidence or logical reasoning. It indicates a high level of probability.
For example, "The ground is wet, so it must have rained."
2. May/Might:
"May" and "might" are used to suggest possibility or uncertainty in deductions. It is very difficult to say whether "may" implies a higher degree of possibility, or if "might" suggests a lower degree because it depends on the context.
For example, "She may be running late because of heavy traffic" indicates a possibility, but
"She might have missed the train" suggests a less likely scenario. But, very often, English speakers exchange these two words and can’t really explain why. We are usually guessing the reason something is happening or has happened.
3. Can't/Couldn't:
These modal verbs are employed to express impossibility or strong disbelief based on evidence. "Can't" is used to indicate a conclusion that is logically impossible, while "couldn't" suggests something that was not possible in the past.
For example, "He can't be at home because his car isn't on the drive." implies impossibility, but
"She couldn't have finished her homework already; it's only been ten minutes!" suggests disbelief in the possibility of completing a task in such a short time frame.
In our lesson we shall look at examples of these words which is the best way to help understand them. By the end of this lesson, you will feel confident in employing "must," "may," "might," "can't," and "couldn't" to make logical deductions in everyday conversations and in your written work.
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