Induction and Deduction

[Jack Flak]

Originally Posted by Orangey

The idea that all inductive arguments are actually deductive arguments with tacit (unstated or assumed) premises is called the "deductivist" position in informal logic. It is a legitimate theory in the field...dissonance is not crazy or incorrect to have made mention of it.

Nor did I say that, or think that. (I may have taken issue with other conclusions in the thread.)

[Evan]

I didn't think you thought that. I was just frustrated because I couldn't word my position in a way that was clear to all y'all.

[Orangey]

Well, "well-known" is a bit relative. I guess you could say it's well-known to the few people who care about informal logic . But yeah, it's called the "reconstructive deductivist" position because the idea is to reconstruct informal (and typically so-called inductive, conductive, or abductive) arguments into syllogisms by making the unstated premise explicit. Basically what you described.

I was going to say more, but I think I need to go to sleep for now (lest I type out something totally incoherent and regret it later).

[Orangey]

Originally Posted by Jack Flak

Nor did I say that, or think that. (I may have taken issue with other conclusions in the thread.)

I was really referring to those who posted elementary definitions of "deductive" and "inductive" as though doing so should clear up any confusion (the assumption being that dissonance has his definitions "incorrect").

[The_Liquid_Laser]

Originally Posted by Orangey

The idea that all inductive arguments are actually deductive arguments with tacit (unstated or assumed) premises is called the "deductivist" position in informal logic. It is a legitimate theory in the field...dissonance is not crazy or incorrect to have made mention of it.

Heh, I've never heard of informal logic until your mention of it. After doing a quick scan of Wikipedia, it sounds like what I'd call "poor man's logic". I.e. a person can make a reasonable argument without formally studying logic, or they can use colloquial language rather than formal language and still have a reasonable argument. It sounds something like this to me. (I may be off.)

Originally Posted by dissonance

One hidden premise in all induction is "the future resembles the past".

This has been bugging me since I've read it. It's quite possible to have induction without an assumption like this. Although for an INxJ the majority of their personal induction probably does use this assumption.

[Magic Poriferan]

Originally Posted by The_Liquid_Laser

Heh, I've never heard of informal logic until your mention of it. After doing a quick scan of Wikipedia, it sounds like what I'd call "poor man's logic". I.e. a person can make a reasonable argument without formally studying logic, or they can use colloquial language rather than formal language and still have a reasonable argument. It sounds something like this to me. (I may be off.)

Well, my logic class talks substantially more about informal logic than formal logic. We did cover a lot of important things for formal logic, but my professor explained that through most of life. It's honestly a more practical skill than formal logic. Not that I dislike formal logic, but it's a bit ivory tower.

Originally Posted by The_Liquid_Laser

This has been bugging me since I've read it. It's quite possible to have induction without an assumption like this. Although for an INxJ the majority of their personal induction probably does use this assumption.

While that's true, I think we can agree that a strong inductive argument does usually work on the premise of some kind of repetition or large numbers. This is known as induction by enumeration. It is simple. and almost surely the most common form of inductive logic used. Sadly, it might be the most common form of logic used by humans in general.

It is true however that there are other kinds of inductive argument, Dissonance, but I would return to Laser by pointing out that they are all very similar to induction by enumeration. Reasoning by analogy, for instance, is still based on the notion that something happening before tells us what will happen now. The fact is, and I think this might be what Dissonance was trying to say, is that for induction to be useful on any complex level almost always requires it to be concatenated with deduction again. The value of statistics heavily lies in the concept of inductive logic, but to get them right, you'll need mathematical reasoning, which is deductive. To ultimately prove that your inductive arguments make more sense than someone else's, you'll have to run the premises through a test of cogency, which will again require deduction.

[Orangey]

Originally Posted by The_Liquid_Laser

Heh, I've never heard of informal logic until your mention of it. After doing a quick scan of Wikipedia, it sounds like what I'd call "poor man's logic". I.e. a person can make a reasonable argument without formally studying logic, or they can use colloquial language rather than formal language and still have a reasonable argument. It sounds something like this to me. (I may be off.)

You've never heard of it? Most critical thinking and even intro to philosophical logic classes are based around informal logic. The study of fallacies? That's part of informal logic.

I don't know what you mean when you say that a person "can make a reasonable argument without formally studying logic, or they can use colloquial language rather than formal language and still have a reasonable argument." It is indeed the study of reasoning in natural language...the type that would be used in everyday examples of argument. People don't reason formally unless they're talking specifically about an issue within a formal language (that is, if we happen to be formal philosophers). Everything else is couched in natural language and in discourse.

The usefulness of studying formal logic (in terms of being able to reason better as a result of having studied it) is yet to be determined...but I would not be surprised if most people didn't really find it useful for "real" argument. The application of formal logic to "real world" argument is its own philosophical issue. In fact, there are some logicians that question whether formal notions of validity even really serve as good models by which to judge correctness in reasoning.

[Evan]

Originally Posted by Orangey

I was really referring to those who posted elementary definitions of "deductive" and "inductive" as though doing so should clear up any confusion (the assumption being that dissonance has his definitions "incorrect").

Thank you!

Originally Posted by The_Liquid_Laser

This has been bugging me since I've read it. It's quite possible to have induction without an assumption like this. Although for an INxJ the majority of their personal induction probably does use this assumption.

Do you have an example? I honestly can't think of one. Applying any trend assumes this, including gravity, making 3d representations out of 2d info, etc.

[The_Liquid_Laser]

Originally Posted by Orangey

You've never heard of it? Most critical thinking and even intro to philosophical logic classes are based around informal logic. The study of fallacies? That's part of informal logic.

All of my logic training comes from a mathematical context, so that is why I'm not familiar with it. Formal logic is very useful within the context of mathematics, but it's true that it's too rigorous to use formally among most people.

Originally Posted by dissonance

Do you have an example? I honestly can't think of one. Applying any trend assumes this, including gravity, making 3d representations out of 2d info, etc.

Example: I hear that five of the people who are taking a piano class are Mary, Betty, Jennifer, Rachel, and Heidi. I conclude that only females take piano class.

[Evan]

Originally Posted by The_Liquid_Laser

Example: I hear that five of the people who are taking a piano class are Mary, Betty, Jennifer, Rachel, and Heidi. I conclude that only females take piano class.

Ah. I see what you're saying.

I guess I would say it's still a hidden premise because you wouldn't make that inference if you hadn't made similar guesses and been right in the past.

Say you're in a universe with 8 possible worlds:
000
001
010
011
110
111
100
101

If you're trying to make an algorithm for guessing the third number from the first two, it's never going to be better than the opposite algorithm. This is a universe in which the future is not necessarily like the past. But if you chop off one of the possible worlds, you can make an algorithm that works, because you assume that the future is like the past, and you're right some of the time.

See what I'm saying?

Maybe my wording of the premise was a bit misleading.