Deduce or Induce? It’s Elementary, Watson …

Whether or not Sherlock Holmes ever said “Elementary, Watson” is debatable. What’s not in question is Holmes’s keen powers of observation that made him a master of deductive reasoning. He was able to deduce, or draw, specific conclusions from general principles. “I deduce that it was the butler with the lamp stand.” (oh, waitthat’s Clue).

The word deduce has a different meaning than induce. Whereas deduce relies on specific conclusions, induce means to derive a general principle from specific observations. Inducing implies more of a supposition.

For example: I might deduce that since all mammals have fur, that creature running across my floor at night is a mammal. That might make me induce that all mammals are very furry. That latter supposition is general rather than specific.

In practical use, deduce appears more often than induce in senses related to drawing conclusions. Induce appears much more often in these uses: (1) to lead to a course of action, and (2) to bring about or stimulate the occurrence of. For example:

  • He deduced that all the women in the room were not his type because they were drinking way too much.
  • Her drug-induced stupor led her to induce her friend to give her a ride home.

Another related word is adduce—which means to offer as example, reason, or proof in discussion or analysis.

  • Here is the mouse I caught. I adduce that is most certainly is a mammal.

Adduce is hardly ever used in daily conversation though. I might deduce that this discussion has given you a headache, and if so, may I induce you to take two aspirin and go to bed?

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    1. I have the same question because so many people use the first one now. I know it to be wrong because “than” implies a degree or level of comparison between 2 things. “Different” does not.

      1. In the example, a repetition of the verb “has” is implied after “induce”, hence “than”. If the sentence began “‘Deduce’ is different…”, then “from” would be used.

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