Why named 'deduction' and 'induction'?



I want to dredge below these two terms; I'm not asking about the definition or concept, which I perceive thanks to http://www.socialresearchmethods.net/kb/dedind.php and my math studies.

How do these two words consist with their respective meanings in logic?


deduce = ...from de- "down" (see de-) + ducere "to lead" (see duke (n.))...


induce: ...from in- "into, in, on, upon" (see in- (2)) + ducere "to lead" (see duke (n.))...

What is being 'lead'? Does the 'down' start at the theory? Why not start 'down' from the observation?

Similarly, why lead INTO the theory? Why not lead INTO the observation?

Couldn't I reverse the direction of the approaches and thus upend these words?


Posted 2014-08-19T14:02:37.090

Reputation: 8 167

Question was closed 2014-08-22T04:16:07.383

3When we use "deductive reasoning", we go "down from" the general idea, the theory to the particulars. When we use "inductive reasoning", we go "up from" particulars to a general idea. We often speak of general ideas as being at a "higher level" than details. If that doesn't make intuitive sense to you, I don't know that it's worth trying to see it. Just accept that someone picked one to be high and the other low. Like why are the Western and Eastern Hemispheres so names? You can go west from the Western Hemisphere and get to the Eastern Hemisphere. It's arbitrary, an historical accident. – Jay – 2015-06-29T21:17:40.063

Interesting question, not entirely clear what you're asking. To deduce is to decrease the number of possible truths. To decrease in number is to go "down" in number. To reduce the possible truths "down" to a single truth is to deduce. You lead the line of reasoning in a direction that logically decreases the number of possible truths. – Ross McConeghy – 2014-08-19T22:58:45.183

6This question appears to be off-topic because it is not about learning English. The OP already understands these words and their usage, and is asking about their etymology out of curiosity. This sort of academic question would be best asked on ELU. – snailplane – 2014-08-21T20:12:57.837

1@snailplane: Another good point. But this OP has a peculiar predilection for asking us to help him "intuitively" understand long-established usages in terms of current syntax, semantics, and familiar figurative usages. Which usually have little relevance to why language changed the way it did many generations ago. – FumbleFingers Reinstate Monica – 2014-08-21T20:56:51.147

1These terms entered English with their meanings already fixed; the question goes beyond English to the figurative use of Latin morphemes by the Romans. – StoneyB on hiatus – 2014-08-22T01:31:57.687



It's an interesting question and I'm afraid my answer will be more about idiom than built on a solid foundation of etymology.

Deduce - each inference leads you another step down the path toward the conclusion. Rivers flow downstream, and in the same way, each logical conclusion flows from the one before it to an inevitable result.

Induce - all of the evidence points to a logical conclusion. I visualize this as a circle of arrows pointing inward to lead you toward the conclusion at the center. The evidence isn't necessarily linked in a sequence, so there is no flow "downstream" to the conclusion.

I think that the direction is always toward (either down or into) the logical conclusion because it doesn't make sense to start with a conclusion and look then for supporting logic when you're trying to persuade someone to agree with you. It's much more natural to get the person being persuaded to agree with some statement first, then show eventually that they must agree with your conclusion if they agree with everything that has come before.


Posted 2014-08-19T14:02:37.090

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