Reasoning It Out — Building a Chain of Deduction

Detective stories are full of deduction — can you follow the clues?

Notice

  • The door was locked from the inside, so he must have used the window.
  • The dog didn’t bark, so it can’t have been a stranger.
  • She might have seen something, we should ask her.

Rule

Combine deduction modals with reasons (because, so, since) to build a full chain of logic — exactly how detectives, doctors, and everyday problem-solvers think out loud.

Practice

  1. The ground was dry, so it ___ have rained.
    Answer: can’t
  2. She left early, so she ___ have been tired.
    Answer: must
  3. I’m not sure, but he ___ have taken the wrong train.
    Answer: might/could
  4. All the lights were off, so they ___ have been asleep.
    Answer: must
  5. He ___ have eaten it, he’s allergic to nuts.
    Answer: can’t

Connect

Read short mystery-style passages and practise deduction language.

Try Reading Quiz →

CEFR: Reading — follow a chain of reasoning in a short narrative or explanatory text.

Azizul Hakim
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