The Problem of Deduction?

[C~G]

Psychology posits that there are intuitive and emotional forms of reasoning. My guess is that people who 'do not get logic' are actually using semi-conscious reasoning based on experience and a poorly characterized estimation of probabilities.

Logic is about trying to be cognizant about one's reasoning, even if it doesn't guarantee reaching true conclusions. So people who 'don't get it' aren't really trying to analyze their reasoning, they're just trying to reach a true conclusion.

They are the same things with "real logical" reasoning.

Psychology in this case can go to hell, since the terms are just blown out of someone's bottom.

Only difference towards knowing "real logic" compared the two other are the strict following of given rules, higher probability of guessing it right since earlier experiences and continuos repetition of this action. Nothing else.

Logical types understand logic "better" because they do it more often and thus look "more" logical.

Duh!

I'm sure this will be eventually proven by brain science. It's simple memory thing really. Those that use more of "emotional" or "intuitional" are just those that aren't used to draw those from their memory for the use. Of course the interesting part is that nothing actually separates the original intuition part of the logic or the more concrete part of logic. They are just set parameters to our brain through studying it over and over again. Sure, people have different kind of brains too and example because of better memory organization it is why some people blossom in this while others are good at something else example being more creative for less organized memory linkage.

What comes to OP question, the Modus ponens is one of the clear principles of logic so only reason it could fail is either brain damage, total lack of concentration or the actual problem's language being so obscure or the question so hypothetical the terms itself become hard to comprehend and calculate.

No wonder the tortoise was confused since it's not normal people to talk about A or B, let alone Z. Usually people talk about real world objects and in case of tortoise, they don't usually even talk.

 

[warpus]

That's an ironic comment seeing as how thus far in the thread, the only person who seems to grasp what is going on is the dude with the philosophy education (Ayatollah). Philosophers have driven a good bulk of the advancements in logic.

I'm grasping it, it's just this sort of question is.. well.. akin to asking a farmer "How do you know that cows produce milk?"

Going back to this:

You still aren't getting the heart of the issue. Suppose I gave the tortoises question to you, and you showed me a truth table. I ask, "why suppose that a truth table at that configuration yields the conclusion?" and you say, "well, look at that freaking box on the truth table!" Ok, so you seem to be asserting the proposition "If such-and-such configuration on a truth table yields a 'T', then that conclusion follows from the conjunction of the expressions in the top of the columns that you are using". So that's another hypothetical proposition to add, and so on and so on. The problem remains.

The issue is that you don't want to make an assumption regarding what things mean..

As soon as you assume that --> means what the truth table says it means, then the problem is reduced to figuring out how to read a truth table, which is trivial.

Believe me, I know what's going on here You're attempting to apply philosophical ideas to formal logic, which doesn't work.

In formal logic sometimes all you need is a truth table, and that's that. Everyone who works with logic assumes the same things, and everyone's happy..

A philosopher comes along and adds unneeded layers of abstraction to the whole thing, and that's when you start getting 'problems'.

 

[Erik Mesoy]

I like this thread. I've seen the problem before and it gets too little attention. *idly baps GoodGame for top-posting*

Is it something that can be explained in normal terms?

Define "normal terms". But I'll try.

What makes "If P implies Q, and P is true, then Q is true" more legitimate a statement than "If P implies Q, and P is true, then Q is false" ?

For that matter, what makes "If P implies Q, and P is true, then Q is true" more legitimate a statement than "If P implies Q, and P is true, then the moon is made out of green cheese" ?

Answers to this normally appeal to meta-logic which is cumbersome to write with quotemarks, and which ends up in the infinite regress described in the problem. Or they appeal to intuition.

No wonder the tortoise was confused since it's not normal people to talk about A or B, let alone Z. Usually people talk about real world objects and in case of tortoise, they don't usually even talk.

WTH has this got to do with anything? Is it an argument from dislike of labels and hypotheticals?

 

[C~G]

WTH has this got to do with anything? Is it an argument from dislike of labels and hypotheticals?

Getting bit of paranoid, are we?

But yes, of course.

I usually camouflage my argumentation in the form of a word play or a joke.

 

[Fifty]

I'm grasping it, it's just this sort of question is.. well.. akin to asking a farmer "How do you know that cows produce milk?"

It bears only superficial resemblance to skeptical theses.

As soon as you assume that --> means what the truth table says it means, then the problem is reduced to figuring out how to read a truth table, which is trivial.

No, it isn't about how to read a truth table. It isn't about what --> means. It's asking why rule of logic dictates that given those premises, I should accept the conclusion. It isn't about the meaning of a conditional at all.

Believe me, I know what's going on here You're attempting to apply philosophical ideas to formal logic, which doesn't work.

Again, more ignorant rambling. You don't seem to understand the question, let alone have a sensible answer to it. Your ramblings about truth tables and the meaning of a conditional are completely immaterial to the point, as you could probably figure out by actually reading what logicians and philosophers have said about the issue. As for your silly little comment about "philosophical ideas", many of the biggest advances in logic were and continue to be a direct consequence of applying "philosophical ideas" to formal logic. I suspect that you just haven't a clue what "philosophical ideas" are, nor what logicians actually do. Here's a hint: They don't sit around making truth tables or doing proofs all day.

In formal logic sometimes all you need is a truth table, and that's that.

But why suppose that the propositions expressed by truth tables yield that conclusion?? Truth tables are just short hand for lists of propositions, the problem does not go away. Truth tables have absolutely nothing to do with anything in this thread, and I haven't the slightest clue why you keep brining them up (other than that truth tables are one of the 1st things that they introduce in logic classes...)

Everyone who works with logic assumes the same things, and everyone's happy.

Say that to a real life logician (and not some dumb kid who's taken math, logic 101, and some comp sci and thus thinks he knows what everything about logic) and see how long it takes before they either laugh or give you a "you're an idiot" look. Many of the greatest advances in logic have come from questioning assumptions and undermining the projects of other logicians. You sound like a freaking Randroid with such comments: "ALLS U HAVE 2 DO IS ESTABLISH SUM AXIUMS THEN APPLY LOGIC LOL".

I'm not sure how much more we can get from this exchange. I'd suggest reading up on what truth tables actually are. You're really not getting the question at all. I'm not saying this to be rude or evasive or whatever, this is just pointless.

 

[Brighteye]

Logic is fundamental and absolute. Its laws are simply descriptions of how truth can be extracted from truth-containing information, not additional assumptions.

If I deny logic I deny all reason, and if I deny reason then everything lacks meaning, because reason is what gives things meaning.

 

[mark_c]

No, it isn't about how to read a truth table. It isn't about what --> means. It's asking why rule of logic dictates that given those premises, I should accept the conclusion. It isn't about the meaning of a conditional at all.

But surely, accepting "A -> B" means by definition that if you accept A, you will accept B. So if you accept A but you don't accept B, then it can't be true you accept A -> B.

This makes about the same sense as saying "What if I believe X is true and I believe X is not true". Yes you can construct these contradictory statements, but if someone actually makes such a statement, I'm not sure there is anything profound going on here.

PS - I would hope that anyone who's studied logic can argue their case without resorting to an assortment of ridiculous laughing smilies. That's not logic, that's immature ridicule.

 

[warpus]

No, it isn't about how to read a truth table. It isn't about what --> means. It's asking why rule of logic dictates that given those premises, I should accept the conclusion. It isn't about the meaning of a conditional at all.

Let's alter your question slightly

Assuming:
1. A (is true)
2. B (is true)
Therefore A OR B (is true)

Same thing, the only thing is that we've now got a different logical relation, right?

So.. how do you convince someone that A OR B given that 1. and 2. ?

Well, you could go:
3. A AND B --> A OR B

But then you can also go:
(A AND B --> A OR B) AND A AND B --> A OR B

just like in your example in the OP...

But so what? You can keep doing this over and over and over, recursively making your statement longer. It's still the same statement. They are logically equivalent.

You stop at the shortest one you can create, plug in truth values for all of your variables, and see what you get as a result.

Your initial example can be (less confusingly) rewritten as:

1) A is TRUE
2) (A --> B) is TRUE
Therefore B is TRUE

Just because you are using an implied (-->) relation as one of your original conditions and forgetting to remind people that statement 2) is true by writing it out in full, and pointing out that you get a neat pattern by recursively adding to the statement, doesn't make it profound in any way whatsoever.

I just did the same thing with a different relation (AND) and ... there is nothing to this. It's just simple logic.

as you could probably figure out by actually reading what logicians and philosophers have said about the issue.

If you can't put it in your own words, then perhaps you do not understand the 'issue' very well yourself.

But why suppose that the propositions expressed by truth tables yield that conclusion??

Why? Let's look at your example again:

1) A
2) A --> B
Therefore B

But let's rewrite it a bit so that it looks a lot cleaner

{A AND (A --> B)} is TRUE

Now, we can use the rules of logic to analyze this statement and try to determine whether B is TRUE, FALSE, or if it could possibly be both.

How do we do this?

Well, you can plug in different things for B to see if the statement holds. It only ends up holding if you set B to TRUE.

You could accomplish the same thing by using a truth table. And yes, you can complain all you want, I will probably bring them up again.

That's simple logic.. Your original post looks deceivingly profound at first, but there is nothing to it at all.

Truth tables are just short hand for lists of propositions, the problem does not go away. Truth tables have absolutely nothing to do with anything in this thread, and I haven't the slightest clue why you keep brining them up (other than that truth tables are one of the 1st things that they introduce in logic classes...)

Right.. I suppose I should duck out of this thread now; I'm obviously not educated enough to be graced by your presence.

Say that to a real life logician (and not some dumb kid who's taken math, logic 101, and some comp sci and thus thinks he knows what everything about logic) and see how long it takes before they either laugh or give you a "you're an idiot" look. Many of the greatest advances in logic have come from questioning assumptions and undermining the projects of other logicians. You sound like a freaking Randroid with such comments: "ALLS U HAVE 2 DO IS ESTABLISH SUM AXIUMS THEN APPLY LOGIC LOL".

I'm not sure how much more we can get from this exchange. I'd suggest reading up on what truth tables actually are. You're really not getting the question at all. I'm not saying this to be rude or evasive or whatever, this is just pointless.

If our exchange is going to be you taking poorly worded quotes of mine (hey, I write most of this stuff at work) and going on silly rants, then no, we probably won't get anywhere.

 

[Fifty]

But surely, accepting "A -> B" means by definition that if you accept A, you will accept B. So if you accept A but you don't accept B, then it can't be true you accept A -> B.

No, that's not true. You are just taking the incredible obviousness of the conclusion and then assuming that that means "by definition" if you accept A than you will accept B. When the tortoise says "I accept A, and I accept A-->B, but then why should I accept B?" He is asking why is it the case that 1 and 2 imply the conclusion??? Now the point is that, unless we want to go into this infinite series of new rules, you have to go "you stupid tortoise! Its just freaking obvious! If you accept A, and you accept A-->B, then of course you have to accept B! You're an idiot if you'd deny something so simple!" The point is, you have to just see that the conclusion follows from the premises. As David Kaplan (famous logician) said (in reference to a different problem), logic is not a stipulative discipline. You just have to "feel" validity. Rambling on and on about truth tables doesn't help at all, because truth tables are just another way of expressing the same exact thing!

This makes about the same sense as saying "What if I believe X is true and I believe X is not true". Yes you can construct these contradictory statements, but if someone actually makes such a statement

No, its not the same as asserting a contradiction. The tortoise isn't asserting any contradiction at all.

Perhaps I can make this more clear by explaining an analogous. Suppose there is some insanely hard deductive proof, such that only a handful of the world's logicians can derive the conclusion from the premises in a systematic manner. Now suppose that we just listed the premises of that argument, and the conclusion of that argument, without writing out the proof. Now its a fact that the conclusion of that argument is entailed by the premises, otherwise there wouldn't even exist a proof. Now supposed I looked at the premises, and looked at the conclusion, and asked one of these brilliant logicians how on earth you got that conclusion from those premises? What is the logician going to do? He's going to say "well fifty, here's the proof! You can see all these great rules of inference I used to derive that conclusion from those premises".

Our case is just like that, but with a far simpler proof. It isn't crazy to ask what rules of inference someone used to get to a conclusion from a set of premises, and it doesn't amount to asserting a contradiction. In the context of extremely hard proofs, in fact, its a perfectly legitimate question to ask. All the tortoise does is ask that about a much much simpler proof! Now, don't get me wrong. I think that the tortoise is wrong in a way that somone asking about the really hard proof isn't. However, its not clear how the tortoise is wrong unless we think that logic really is about "just getting it" (aka logical intuition).

PS - I would hope that anyone who's studied logic can argue their case without resorting to an assortment of ridiculous laughing smilies. That's not logic, that's immature ridicule.

I'm sorry, I really am, its just that every time I make a thread about something interesting that involves logic, science, skepticism, morality, etc., the same 2 or 3 people come around and bark a bunch of inane sophomoric garbage about logic that betrays a complete lack of a clue. It is aggravating to have to spend so much of these threads explaining a really elementary problem to people who just don't seem to get it. My hopes were that this thread would involve more people like Ayatollah and Erik (that is, people who aren't morons) posting their views on what's going on with this, not me sitting around trying over and over and over to explain what the problem is to people who are evidently just too obtuse to get it, and whats worse, they don't just drop by for a one-liner and a wink smiley like the new-agers, they infest the entire thread with their idiotic jabberings to the point that the actual purpose of the thread gets lost. I didn't want this thread to fall apart into "OMG JUS DRAW A TROOF TABLE!!!!", I wanted it to be at thread where people who actually understand the problem post their views on it. I got two good responses (thanks Ayatollah and Erik!), and that's it.

Moderator Action: TRolling - warned.
Please read the forum rules: http://forums.civfanatics.com/showthread.php?t=422889

This stuff is genuinely interesting to me, and I like discussing it. Imagine if you were interested in basketball, and you made a thread to discuss views on what the best sort of defense is, and then you had to spend the entire thread explaining to people what the rules of the game were, and they just outright refused to get it. You'd probably get pretty darn annoyed!

 

[LightFang]

Well I'm not qualified to even begin to talk about the question, but I have to admit that the Lewis Carroll passage was very interesting. I had never thought of that problem before. Logic is interesting, but just not my forte at all.

Although I don't understand this harping of truth tables. That I can understand. If it really were that easy, wouldn't it have been solved by now? Heh.

Isn't this like an axiom thing? Like, rules that you just accept naturally as intuitive or whatever?

 

[WillJ]

This is a question that I always wondered about ever since being introduced to the world of logic (specifically in geometry class in 9th grade) but was always too afraid to ask. I am actually incredibly excited to see that real philosophers take the question seriously, i.e. I'm not crazy.

"You just have to see it" is not a satisfactory answer. "You just have to see it" is how a Christian might justify his faith, but even the most ardent Christian will admit that

1) A
2) A --> B
Therefore B

occupies a plane of certainty that Christianity does not.

At the same time, there has to be some degree of intuition involved. You can't boil away all the intuition with formal logic, lest you end up answering a tortoise's infinite questions. But you do have to recognize that this intuition is an intuition like no other; we know empirically that if you present the above argument to anyone comfortable with abstraction, no one will deny it --- philosophers say that someone could, but no one ever does, a fact that should surely be significant even to a philosopher. Studying the psychology of this might be illuminating (or maybe it's irrelevant).

 

[Erik Mesoy]

"You just have to see it" is not a satisfactory answer. "You just have to see it" is how a Christian might justify his faith, but even the most ardent Christian will admit that

1) A
2) A --> B
Therefore B

occupies a plane of certainty that Christianity does not.

[...] But you do have to recognize that this intuition is an intuition like no other; we know empirically that if you present the above argument to anyone comfortable with abstraction, no one will deny it[...]

You need to read more FSTDT.
http://www.fstdt.com/fundies/Default.aspx

"Make sure your answer uses Scripture, not logic."
"You are banned. You are not a Christian for Christians don't accuse brothers and sisters in Christ of being non-Christian."

Be more cynical.

 

[brennan]

But surely, accepting "A -> B" means by definition that if you accept A, you will accept B. So if you accept A but you don't accept B, then it can't be true you accept A -> B.

This makes about the same sense as saying "What if I believe X is true and I believe X is not true". Yes you can construct these contradictory statements, but if someone actually makes such a statement, I'm not sure there is anything profound going on here.

PS - I would hope that anyone who's studied logic can argue their case without resorting to an assortment of ridiculous laughing smilies. That's not logic, that's immature ridicule.

Yes, yes and yes.

But so what? You can keep doing this over and over and over, recursively making your statement longer. It's still the same statement. They are logically equivalent.

If you can't put it in your own words, then perhaps you do not understand the 'issue' very well yourself.

Yes and yes.

No, that's not true. You are just taking the incredible obviousness of the conclusion and then assuming that that means "by definition" if you accept A than you will accept B ... The point is, you have to just see that the conclusion follows from the premises...No, its not the same as asserting a contradiction. The tortoise isn't asserting any contradiction at all.

What is wrong with accepting a definition? You are always free to show that it is wrong. It seems to me that there is clearly a contradiction in saying you accept a proposition and then rejecting a conclusion based upon that very proposition. Again, show the conclusion to be wrong and you then have a basis for stating that you do not accept the proposition and that logic has a problem. This is not the case.

Perhaps I can make this more clear by explaining an analogous. Suppose there is some insanely hard deductive proof, such that only a handful of the world's logicians can derive the conclusion from the premises in a systematic manner. Now suppose that we just listed the premises of that argument, and the conclusion of that argument, without writing out the proof. Now its a fact that the conclusion of that argument is entailed by the premises, otherwise there wouldn't even exist a proof. Now supposed I looked at the premises, and looked at the conclusion, and asked one of these brilliant logicians how on earth you got that conclusion from those premises? What is the logician going to do? He's going to say "well fifty, here's the proof! You can see all these great rules of inference I used to derive that conclusion from those premises".

False analogy. There is no such hidden mechanism in A -> B, merely an acceptance of how -> works. This is either 'obvious' (because your mind handles logical structures well) or demonstrably true by the simple virtue that it always works. Throwing a rather nebulous 'yeah but why?' at it is meaningless.

If you reject the conclusion then you are not accepting the proposition A -> B.

tbh insisting this is a problem is a philosophical dead-end similar to asking why is blue blue? Just because you can ask a question does not give that question meaning. Why do people keep trying to sweep logical positivism under the carpet?

I see you still haven't learned to accept that intelligent and educated people can disagree with you without spewing insults and smilies around. Sad.

 

[C~G]

I'm sorry, I really am, its just that every time I make a thread about something interesting that involves logic, science, skepticism, morality, etc., the same 2 or 3 people come around and bark a bunch of inane sophomoric garbage about logic that betrays a complete lack of a clue. It is aggravating to have to spend so much of these threads explaining a really elementary problem to people who just don't seem to get it. My hopes were that this thread would involve more people like Ayatollah and Erik (that is, people who aren't morons) posting their views on what's going on with this, not me sitting around trying over and over and over to explain what the problem is to people who are evidently just too obtuse to get it, and whats worse, they don't just drop by for a one-liner and a wink smiley like the new-agers, they infest the entire thread with their idiotic jabberings to the point that the actual purpose of the thread gets lost. I didn't want this thread to fall apart into "OMG JUS DRAW A TROOF TABLE!!!!", I wanted it to be at thread where people who actually understand the problem post their views on it. I got two good responses (thanks Ayatollah and Erik!), and that's it.

That my friend is a troll.

There's no point to report that since I just feel sorry for you.
Moderator Action: Accusing someone of trolling is trolling as well - you aren't a moderator. Next time, DO report it.


Please don't troll your own thread if you are unable to make clear enough question what the thread is about. And I agree with brennan, it's kind of sad that your grand philosophical wanderlust ends in the moment you step out of the door as you start hurling insults like a child that doesn't get straight answer from parents why sky is blue. "No, I'm not meaning the effects of light reflection or anything like that, but WHY?!!!!"

The questioning is sometimes adorable quality for a child since it shows how curious he is about the world and probaby extremely valuable quality for a philosopher but combining that with insults kind of shows how weak the original stance is. One sweep and you're down.

Answers to this normally appeal to meta-logic which is cumbersome to write with quotemarks, and which ends up in the infinite regress described in the problem. Or they appeal to intuition.

This probably becomes closest probably what you are asking.

But my question is what true answer doesn't end up being infinitive regress if challenged or require "the intuitive" understanding?

Because there it always boils down to. Where the unconscious effort of our brain stops and our seemingly conscious effort begins. You're talking about kind of intutitive jump start and where it comes from.

What you are asking is just intuition pump as Dennett would describe it.

Or question about what makes an apple and apple. OH MY GOD, There's some kind of intuitive twitch involved but it's at the same time logical!

But of course I'm as lost here as rest of bunch here except Erik and Ayotallah. Maybe they are in your "level" and worthy of enough to discuss this very very difficult problem.

Bottomline: Answering it would require not knowledge of logic or philosophy but knowledge more of brain science and this organ's technical qualities that are related to our experience. It probably has to do (like many other things) with simple pattern recognition of continuos pattern. We learn some things are similar/dissimilar and related/unrelated and then after we have succesfully combined data that where there's action between these kind of two objects it leads to the third option and so on and so on. The intuitive part probably is just your memory doing double check and a sommersault when it got it right.

Or just maybe the brain draws truthtable and just picks out that seems to be the most handy, oh wait!

 

[Brighteye]

In my experience, the people who whine most about others not having sufficient education in philosophy are the ones who have least to say, and make up for it by using excessive jargon or dismissing a view without argument simply because a pet philosopher has dismissed it.

When you ask a question such as 'Why is logic valid?' it doesn't require years of study to answer. It's a question that applies to everyone, and doesn't rely on background knowledge. In fact, one of the appeals of philosophy to many people is that philosophy is the background on which to base further thought and knowledge.

 

[mark_c]

No, that's not true. You are just taking the incredible obviousness of the conclusion and then assuming that that means "by definition" if you accept A than you will accept B. When the tortoise says "I accept A, and I accept A-->B, but then why should I accept B?" He is asking why is it the case that 1 and 2 imply the conclusion??? Now the point is that, unless we want to go into this infinite series of new rules, you have to go "you stupid tortoise! Its just freaking obvious! If you accept A, and you accept A-->B, then of course you have to accept B! You're an idiot if you'd deny something so simple!" The point is, you have to just see that the conclusion follows from the premises.

Or you could say that this is the definition of "A -> B" - why is that wrong? There's nothing obvious about it, it's just what it means. We could perhaps break it down into some more fundamental steps, but somewhere along the line you start off with axioms which are assumed to be true, and definitions which are agreed upon.

 

[Fifty]

But you do have to recognize that this intuition is an intuition like no other; we know empirically that if you present the above argument to anyone comfortable with abstraction, no one will deny it --- philosophers say that someone could, but no one ever does, a fact that should surely be significant even to a philosopher.

Yea, I mean nobody thinks that this is a problem for logic in the sense of like "oh no! logic is unsubstantiated!" Rather, its just an interesting question to wonder how the tortoise is wrong. And unless one appeals to a "logic intuition", and say that the tortoise has an incorrect logic intuition, I don't see how one could claim that the tortoise is acting wrongly. He's not denying any premises, he's just asking "why are rules of inference true?" The proposition "B" is a distinct proposition, and asking how one distinct proposition logically follows from two other distinct propositions does not seem, at least on the face of it, a wrong question to ask.

While I said that the problem isn't a problem in the sense that it like hurts logic or something, it is a problem in that it bears on other areas of philosophical interest. For example, there's this debate in epistemology about whether knowledge is closed under deductive inference. That is, whether if you know that (P & (P --> Q)), you are always in a position to know that Q. While it would seem obvious that you do, there are actually some substantive arguments claiming otherwise! In one particular area of the closure debate, the question of where you come down on this Achilles/Tortoise dialog will affect how you feel about that area.

Thanks for the intelligent reply, that makes 3 in this thread!

I see you still haven't learned to accept that intelligent and educated people can disagree with you without spewing insults and smilies around. Sad.

I don't see any intelligent and educated people disagreeing with me in this thread So far, we have a few people who are dim enough not to understand a problem that people can understand in junior high (well at least people like WillJ ), who think it has to do with either the meaning of --> or truth tables, both of which are utterly bizarre statements to make. What's worse, I'm just not a good enough writer to dumb the question down enough so that you and warpus and company will get it. What's sad about it is that you guys seem to take a great deal of pride out of your self-perceived grasp of logic. What's annoying is that you guys ruin threads with your jabbering. Of the three people who actually get it, I've been perfectly polite. And its not just a matter of "hating those who disagree with me" either. There's a lot of philosophical issues in which I disagree with the views of FredLC, or Plotinus, or Ayatollah, Perfection, WillJ, Erik, Mise, etc.. However, I will always be respectful about it, because for them "disagreement" doesn't amount to "I don't get it so I'm going to spew random crap and pretend I've solved the problem", which is what it amounts to for you guys. And not all of them even have a philosophy education, its just a matter of being intelligent enough to not require 40 pages of explanation to grasp relatively simple issues. Plus, the hubris of you guys is astounding. You are taking something that is recognized as a problem not only to anybody who is moderately intelligent, but to tons of incredibly brilliant logicians, and giving these simplistic answers that are just obviously wrong, yet confidently thinking that nothing is actually going on!

The reason I do get annoyed and start being trollish towards you guys is that the combination of "I want my threads to be interesting" and "I am not a good enough writer to dumb this down to the point that you guys will either understand it or shut up and stop posting" is somewhat aggravating.

When you ask a question such as 'Why is logic valid?' it doesn't require years of study to answer.

Nobody is asking 'why is logic valid'.

Or you could say that this is the definition of "A -> B" - why is that wrong?

But "-->" doesn't mean "if you accept the antecedent then you must accept the consequent". It means "if the antecedent is true than the consequent is true". While the incredible obviousness of the inference makes it seem to be a matter of "meaning" or "definition" for us normal people, it really isn't. Drawing the person a truth table means absolutely nothing, because a truth table just expresses the same propositions in a different way.



Could you guys who just can't get it stop posting in the thread? You can even believe that you've solved it, I don't care. Pretty please?
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Please read the forum rules: http://forums.civfanatics.com/showthread.php?t=422889

 

[Brighteye]

Nobody is asking 'why is logic valid'.

Could you guys who just can't get it stop posting in the thread? You can even believe that you've solved it, I don't care. Pretty please?

You are asking why the rules of inference are rules that govern us without our consent. You're asking why we should accept what inference tells us to accept.

I thought that inference was part of, if not all of, logic. Hence to question whether inference is 'true' is questioning logical 'truths'.

Of course, as a philosopher you have a very strict definition of valid. Since I'm using English, I could have meant any of these (OED):
1. Good or adequate in law; possessing legal authority or force; legally binding or efficacious.
2. Of arguments, proofs, assertions, etc.: Well founded and fully applicable to the particular matter or circumstances; sound and to the point; against which no objection can fairly be brought
b. In general use: Effective, effectual; sound.

Now as I see it, you're questioning whether (a part of) logic is a universal rule that holds whether we accept it or not.
Since no-one can prove that it does, you suppose that we must base our use of it on something else.
You suggest that we use intuition as a basis for it.
You could then argue that intuition is a sufficient basis for argument or theorising.

I'd suggest that if logic is not universal, then we have no sensible basis for using it, as you point out. I'd disagree that intuition must be sensible, even if it's out only basis for logic.
Given that intuitions can be conflicting, intuitions cannot be a sensible basis for teasing out truth, because we assume that truth cannot conflict with itself.
So basing (our current rules of) logic on intuition is illogical, and not coherent.

If we must have a basis for logic, and we have ruled out the only alternative to it being universal, we accept it as universal. That's consistent.

Because you've read all the thought on this subject, you'll be able to tell me why this is wrong.
If you know that the question cannot be solved, because professional philosophers haven't solved it, and you also know that you know more than anyone else here, because you've read about it, why would you care to discuss it further?

 

[Riffraff]

Could you actually avoid the problem with a 'better' formal system, perhaps regarding the linking of statements?

Or would the answer be obviously not or else we'd be using that system...

 

[brennan]

I don't see any intelligent and educated people disagreeing with me in this thread

More of your inane trolling?

...Plus, the hubris of you guys is astounding. You are taking something that is recognized as a problem not only to anybody who is moderately intelligent, but to tons of incredibly brilliant logicians, and giving these simplistic answers that are just obviously wrong, yet confidently thinking that nothing is actually going on!

Might I suggest that instead of these ad hominem attacks on your respondents your actually respond to what they say. We might all start to think you didn't actually understand the replys...

Plus it's kind of ironic that you're saying we are 'obviously wrong' btw.

The reason I do get annoyed and start being trollish towards you guys is that the combination of "I want my threads to be interesting" and "I am not a good enough writer to dumb this down to the point that you guys will either understand it or shut up and stop posting" is somewhat aggravating.

Sorry, but I think the real problem is that you don't understand some of the answers you are being given Fifty. I can see precisely what you are getting at, and to me it is because you are making a simple mistake with language and definitions.

But "-->" doesn't mean "if you accept the antecedent then you must accept the consequent".

It's a little package Fifty, it suggests that a conclusion follows from a condition being met. If you 'accept' that then you can't just say 'yeah but why' and refuse to accept the conclusion, it's all built in. If it didn't actually work it wouldn't get used, there's no problem unless you can demonstrate it to be wrong.