Induction/deduction

Question

HelloCould you please tell me the difference between "induce(induction) and deduce(deduction)"I could not understand their differences by checking the dictionary.Also I'd like to know the difference between "a posteriori" and "a priori" I think these two are related to my previous question as well.

JohnParis · Accepted Answer

a priori = knowledge that you get from theory, not actual experience.

a posteriori = knowledge that you get from your own experience or have seen for yourself.

To induce means to succeed in persuading or influencing (someone) to do something.

Example: The amount of people demonstrating at the front gate of the factory induced many workers to stay at home.
To induce also means to bring about or give rise to.

Example: None of the measures taken by the strikers induced a change of policy.

To deduce means to arrive at a fact or a conclusion by reasoning.

Examples: Very little can be safely deduced from the figures you have provided concerning the ability of the airplane to fly. After taking water samples and studying their content, they deduced that the fish died because of chemical pollution.

John

Mister Micawber · Answer

Induction is reasoning from the specific to the general: I'm bored in this class, so everyone in class must be bored.

Deduction is reasoning from the general to the specific: Everyone in the class looks bored, so I must look bored, too.

A posteriori = reasoning after the fact. This class was boring, so a posteriori this subject is boring.

A priori = reasoning before the fact. This subject sounds boring to me, so a priori the classes will be boring.

I stand open to criticism by the philosophers among us.

Mister Micawber · Answer

Ah, John beat me to it while I was still cogitating.

JohnParis · Answer

TheSiavash

MM's definition and examples of deductive and inductive reasoning are probably closer to what you are seeking compared with mine.

John

CalifJim · Answer

TheSiavashCould you please tell me the difference between "induce(induction) and deduce(deduction)"

Induction. (Reasoning from empirical observations.)

That dog has four legs. Hmm. That other dog has four legs too. Hmm. That other dog has four legs too. Hmm. And so does that one - and that one - and that one - and that one.

Conclusion: All dogs have four legs.

In short, induction is reasoning that if something is true for very, very many cases of the same kind, it must be true for all cases of the same kind. In other words, you reason from specific cases to generalities. This version of induction is not foolproof because there could always be an exception you haven't yet encountered, but see 'mathematical induction' below, which is foolproof.

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Mathematical induction. A second look at induction.

Suppose you can prove a theorem for the case when x = 1.

Suppose further you can prove that no matter which x the theorem holds for, it will also hold for x+1.

These proofs taken together prove that the theorem holds for all whole numbers.

This is like saying that if you know you are capable of getting onto the first step of a staircase, and you know that no matter which step you are on, you can get to the next step above, then you have proved that you can ascend the staircase as high as you like without limit.

Again, the basic outline is reasoning from specific cases to generalities. This is a posteriori reasoning.

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Deduction. (Syllogism)

All dogs are four-legged animals. < major premise

My sister has a dog as a pet.

Conclusion: My sister has a four-legged animal as a pet.

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Deduction. (Symbolized differently)

If p, then q.

p

Therefore q.

That is,

1. If your pet is a dog, then your pet has four legs. < major premise

2. Your pet is a dog.

Conclusion: Your pet has four legs.

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However it is symbolized, deduction is reasoning from an accepted generality to a specific case. This is a priori reasoning. It is specifically the major premise that is the a priori 'fact' on which the conclusion is based.

You can't deduce anything useful unless you have a major premise that you already accept on the basis of induction.

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CJ

Regards · Answer

CalifJimIn short, induction is reasoning that if something is true for very, very many cases of the same kind, it must be true for all cases of the same kind. In other words, you reason from specific cases to generalities. This version of induction is not foolproof because there could always be an exception you haven't yet encountered, but see 'mathematical induction' below, which is foolproof.
CJ

Hi,

CJ, do you know a philosophical question called the problem of induction?

If you do, you probably know it proves that even inductive reasoning can't be completely foolproof.

Regards

TheSiavash · Answer

Thanks EVERYBODY..

that was "differences of induction and deduction for dummies"

Induction/deduction

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