Deductive and inductive reasoning

Re: Deductive and inductive reasoning
Sure they can. An argument can take the form of a deduction (i.e. the conclusion is guaranteed if the premises are true) but still be weak (i.e. the premises aren't true).

1. All chickens have 14 eyes.
2. Cookie Monster is a chicken.
3. Therefore, Cookie Monster has 14 eyes.


This is a deductive argument because the truth of the conclusion is guaranteed if the premise is true, but it's a weak argument because the premise isn't true.

Alright, thanks. Do you mind if I use that for my example in class?

Nope... go right ahead.

C'mon.....you can find your own example for this question can't you?

I am having a hard time following this. If the primises aren't true in a deductive argument, wouldnt that make it a inductive? lol

Everyone who drinks only speaks the truth. Josh is drinking and speaking, therefore he is speaking the truth.


alright. I get it!

The teacher has given an exercise which is designed to distinguish between "truth" and "validity".

Deductive logic can only deal with "validity" since it is concerned with the structure if the argument, not the "truth" of the premises. Indeed Godel showed that all systems(of argument) inevitably included at least one axiom i.e. a statement whose "truth" is assumed. . Technically there are no "weak deductive arguments" only "weak premises".

The cookie monster argument is perfectly valid, irrespective of its truth, since it is in the form of a syllogism. Induction on the other hand goes from the particular to the general, which is deductively invalid, and brings in the additional concept of "probability".

E.g. The sun rose yesterday and every day previously in human history, so the sun will rise today.

Induction is about expectancies of observation, i.e. "predicted truths".

As Fresco points out, what makes an argument deductive or inductive has nothing to do with the truth value of the premises; rather, it has to do with the nature of the conclusion. A deductive argument is one in which the conclusion is guaranteed if the premises are true, while an inductive argument is one in which the conclusion is deemed likely if the premises are true. Or, to put it as Fresco did, a deductive argument is one that begins with generalizations ("All chickens have 14 eyes") to arrive at particulars ("Cookie Monster has 14 eyes"), while an inductive argument is one that begins with particulars ("The sun rose yesterday morning") to arrive at generalizations ("The sun rises every morning.")

Conversely, whether the truth value of the premises determines the validity of the argument but not the type of argument.