I am still a bit puzzled by your questions, particularly coming from you. What is wrong with the responses given in a typical introductory logic textbook?
The 'answer' that can be found in a logic textbook is pretty much some vague considerations that seem to stem from the intention theory. But I'm questioning that theory, so this result does clearly not work. This problem is not discussed in any logic textbook that I have read or skimmed through. (I have not read Copi's.)
4. No, unless you mean that part of a lengthy argument (that is really a series of arguments) is inductive, and part is deductive.
Re 3. Not sure about that. Arguments need to be given. I know that this is a common assumption but is it a good assumption?
Re 4. That's not what I mean.
Also, on further reflection. Skip the second part of question 2 as it is not very relevant here. The discussion about cogent and strong inductive arguments is not what I intended
this thread to be about.
When I write "valid" I always mean "deductively valid". I don't think there is a term that is called inductive validity.
A deductive argument is an argument where the conclusion follows necessarily from the premises.
A valid deductive argument is a deductive argument where the conclusion follows necessarily from the premises.
A non-valid deductive argument is a deductive argument where the conclusion does not follow necessarily from the premises.
First, your definition of deductive argument is identical
with your definition of valid deductive argument. According to you, then, we have no need to speak of valid deductive arguments because all deductive arguments are valid.
Second, you are contradicting yourself. Look at your first and third statement. An invalid deductive argument is according to them both one where the conclusion necessarily follows from the premises and one where it does not. That is impossible.
Also, I dislike that definition of validity very much as it is dangerously ambiguous and causes people to make modal fallacies. There are many logically equivalent definitions of validity. In this thread I stipulate that we use this one:
[INDENT]An argument is valid iff the corresponding conditional is a necessary true proposition.
An inductive argument is an argument where the premises offer a degree of support for the conclusion, but do not necessarily entail it; there is no guarentee (like your article noted).
Careful. Do you accept Ken's view (=intention theory)? If so, then some inductive arguments are valid, because some arguments are intended by the speaker to be inductive but are actually valid.
I think it depends how we use the word "argument". But, I think if we use the word formally, the answer is yes.
This needs some defending.
Do you see how many ways this question can be interpreted?
1.) Yes, some arguments are deductive, some arguments are inductive.
2.) Yes, some arguments (like Pyrrho noted), can have inductive and deductive parts.
3.) No, if you mean that only some arguments are inductive or deductive. Because all formal arguments are deductive or inductive (and you might mean this since this question comes after the one which specifies "all arguments").
Yes, but there is only one good interpretation, and it is straightforward. I even removed extra words that made it even easier to get it right. I suppose I should have left them in. You can insert the word "both" into the question if it is unclear to you, like this:
4. Are some arguments both
deductive and inductive?
In the formal english language, E:
4F. Does there exist an argument such that it is deductive and it is inductive?
(I invented some 'formal machinery' (Ken's phrase) for questions to be formalized. In this the question has the form (∃x)(Dx∧Ix)? Let's not discuss this invention in this thread but some other time. The interested reader can look here
That is not difficult. Deductive arguments are intended to be conclusive arguments by the arguer. If the argument is not conclusive, but is intended to be conclusive, it is a failed (invalid) deductive argument. On the other hand, if an argument is not intended to be a conclusive argument by the arguer, it is non-deductive. But if the premises fail to support the conclusion of the non-deductive argument, then it is a failed (weak) non-deductive argument.
However, whatever the arguer intends, deductive or non-deductive, there are some arguments which it would hardly make sense to intend it as deductive, since it is so clearly non-conclusive; or make sense to intend it as non-deductive since it is so clearly conclusive. It would be a good rule (I think) to count a valid deductive argument as deductive, and a strong non-deductive argument as non-deductive.
This is a good answer from someone defending the standard intention theory. I used to agree with this now I have doubts.
Why do you think it would be a good rule to count a valid argument as deductive even though it is according to that theory inductive?
I assume this is what you meant and you were just being careless when you inserted the word "deductive" there. Otherwise you were merely suggesting that we count valid deductive arguments as deductive. That is not very interesting.
But can't we distinguish between inductive and deductive arguments without considering the intent of the arguer at all?
Not according to the intention theory. This implies that the difference between a deductive argument and an inductive argument is merely
a psychological one and not a logical one. Some people consider this implausible, me included. See the other threads.
I don't see how, although, as I said, there are pretty clear cases of both kind when it would be implausible for the arguer's intention not to be the one or the other. In those cases we have what, in legal jargon, we might call, "constructive intent". That it was the arguer's intent whether or not it actually was (or the arguer was confused).
I agree with this. But even though it is implausible that the arguer intended a given argument to be inductive, it does not follow that it is deductive. Some arguers are terribly confused.
But we can distinguish an inductive argument from a deductive argument by looking looking at the argument. If all the premises can be true without the conclusion being true, it is an inductive argument:
1.) Socrates was Greek
2.) Most Greeks eat fish
3.) Socrates ate fish
This is an inductive argument. And we know it's not a deductive argument because although the premises may be true, the conclusion does not follow necessarily from the premises; the conclusion may not be true.
Isn't that right?
Now you have defined inductive argument as invalid argument. That's another theory and it is inconsistent with the intention theory. Let's call this theory for the validity theory, for it defines deductive argument as valid argument, and inductive argument as invalid argument.
This theory has the curious and implausible implication that all deductive arguments are valid, indeed, they could not be invalid. Thus, one cannot fail to make a valid deductive argument, it is impossible. This is the position that Kritikos was defending and to which Ken gave the plausible example arithmetic analogy. See the opening post.
I would rather say, we do not know what the argument is without knowing the intentions of the arguer. But once we know what the argument is, we then may be able to determine whether it is deductively valid or not, and whether it is inductively valid or not.
Perhaps, though, this is a mere verbal distinction, without any importance at all.
Not at all! This is the crucial point. In this post you are endorsing the intention theory. That's fine, but the theory has its problems some of which I have mentioned already.
I thought what you were meaning to ask for is an analysis of deductive arguments and/or an analysis of inductive arguments. You already know the difference between the two, so you do not need an explanation of what each is. Instead, what you want is an analysis, for merely knowing the difference between the two doesn't therefore imply that you can always be given an argument and definitively determine whether or not the logical argument is a deductive argument or inductive argument, for sometimes, being privy to the argument is insufficient information to determine whether or not an argument is deductive or inductive.
That of course has no bearing on whether or the argument is deductive or inductive, just as truth doesn't depend on knowledge of the truth.
I don't think you should ever regard inductive arguments as valid or invalid.
You are getting the point. I'm not sure that I know the difference between them. I can make the distinction in practice like any person trained in logic can, but that does not imply that I know the difference, does it?
But I am definitely asking for an analysis.
" I don't think you should ever regard inductive arguments as valid or invalid.
" Why do you think this? Given pretty much any definition that you choose of validity, it is applicable to inductive arguments.
According to the validity theory, all deductive arguments are valid and all inductive arguments are invalid.
According to the intention theory some deductive arguments are valid and some are invalid, and some inductive arguments are valid and some are invalid.
I got soundness and validity confused. Validity speaks nothing of truth, only form. To be valid means that the conclusion follows from the premises. An argument being valid does not mean that it is true. Validity is a necessary but not sufficient condition for soundness. It is not a sufficient condition because an argument not only needs to be valid to be sound, but it also needs to be true.
Is this right?
It is nonsense to speak of true/false arguments.
Validity has something to do with form, but not all valid arguments have a valid form. But this is a discussion I would rather not elaborate on now. You can read more about it in Possible Worlds
where it is discussed at length.
No arguments are either true or false. Are you, perhaps asking whether a valid argument must have a true conclusion. The answer is, no. The same for whether a valid argument must have true premises. But, what is true is that any valid argument with true premises must have a true conclusion.
It is also nonsense to say that no arguments are either true or false. The correct wording is:
Ah, arguments cannot be said to be true or false, just valid or sound, right? Premises and conclusions are what we apply the properties true and false to.
But this is also a side discussion about meaning and category errors. Let's not discuss that now.
Right, because premises and conclusions are propositions (statements) and only propositions (statements) are true or false.
Not sure about that. Maybe we should not assume a propositional theory of truth bearers in this thread. Or, better yet, let's assume it so far (pretty much everyone in this thread holds that theory anyway), and maybe after we have considered the problems of deductive and inductive arguments in that light (so to speak), we could consider them in the light of say a sentence theory of truth bearers.
At least, let's not discuss theories of truth bearers in this thread.
A necessary condition for a sound argument is not that the conclusion be true, although, if an argument is sound, then the conclusion will be true. Truth, then, is a consequent of soundness.
You got yourself confused. It is a necessary condition for soundness. But it is not a sufficient. For this thread let's define soundness like this:
[INDENT]An argument is sound iff:
1. All the premises and the conclusion are true.
2. The argument is valid.
All cogent arguments are strong arguments, but not all strong arguments are cogent arguments, for all cogent arguments are strong arguments with true premises, and not all strong arguments have true premises.
This strongness you speak of is not a standard term as far as I know.
That is not what it says at Wikipedia:
Cogency - Wikipedia, the free encyclopedia
You may use the term differently, but this only reinforces my point that the terms used to describe various inductive arguments are not very standardized.
I edited the Wikipedia page to its current form (I think). I did it because it was terribly confused before. I also inserted the reference to Fallacyfiles. But bear in mind what Ken says:
Actually, some logic books use the term "cogent" to mean, "known to be true", and not just true. So, a cogent argument would be one where the premises are not only true (and argument valid) but are known to be true, so the conclusion is known to be true. But the books differ on this.
Correct. I seem to recall writing this on Wikipedia but they may have changed it. Wikipedia is not a good source for such specific information as this.
But let's not derail the thread with more discussions of cogentness and strongness and what have we, that is, terms related to inductive arguments.
What is a valid inductive argument anyway?
See the definition of validity above. (And please for the love of god (you do believe in god, right?) stop changing the fonts!)
I dont know if you guys have answered the Op or not but I'll throw out some ideas on the subject.
Deductive arguments have true premises and a conclusion that necessarily follows. While inductive arguments have conclusions that are probable, but not necessary. So me thinks inductive arguments hinge on logical possibility while deductive arguments dont. So its impossible to have a counter example to a deductive argument. Does that work emil?
Your first two claims are wrong. I don't know about the rest as they are too vague to consider true or false.