what are the differences between induction and deduction?

Question

Also was Was Watson right when he characterized Sherlock Holmes' inferences as "deductions".

Answer 1

With induction, you start with the big idea and try to determine what details must logically follow from that. For example, Jason is a nice guy, thus he probably does nice things like letting people into traffic and getting his mom flowers for mothers day.

With deduction, you start with little details and build to the big conclusion. If you discover that Susan's car is messy, her coworkers report that her office is always a cluttered mess, and you see health inspectors quarentine her house, you can deduce that she is a slob.

I haven't read enough Sherlock stories to have an opinion as to whether he was making deductions or just good guesses.

Answer 2

Deduction is applying the rules of logic to derive conclusions from other facts.

Induction, notwithstanding the important mathematical technique of "proof by induction", is often construed to mean something different from deduction, namely coming to a conclusion based on the preponderance of evidence.

Now, there's a lot of wiggle room about what's a "fact" and what's merely a strong, well-grounded belief, but it's fair to say that what Sherlock Holmes was using was deduction. Please note, however, that he lived in a fictional world, and that in real life things are messier and "deduction" of that kind would usually be less precise and more like induction.