POLL on the logical validity of an argument on Joe being a squid

[fast]

...

Hey, man, we could infer anything from that, and validly, you know?!
EB

Someone texted me and my dumbass responded here! Too funny!! So, I quickly made it go away.

 

[Angra Mainyu]

in pure mathematics, we only find knowledge of logical truths. In order that such a knowledge be possible, it is necessary that there should be self-evident logical truths, that is to say, truths which are known without demonstration. These are the truths which are the premises of pure mathematics as well as of the deductive elements in every demonstration on any subject whatever.

Good point, Bertrand! That's very perspicacious and quite literally obviously true.

However, how could one admit that self-evident logical truths are indeed necessary to any logical reasoning whatever, including the one necessary for mathematics and science to exist at all, and nonetheless deny that human beings have an intrinsic logical capability; or deny that this logical capability is the only reference we have; or deny that therefore any formal logic has to be at least consistent with it?
EB

To clarify the matter to readers - given that that looks like an attack against me and maybe other posters, even if you do not name us -, what you say above is not at all related to what I have said, or indeed to what anyone has been arguing. That is your invention, even if you fail to realize that. So, of course, I am not at all denying that humans (normally functioning ones at least) have a capability for logic, even if human intuitions on the matter are often flawed. A formal logic does not need to follow the flaws of the human ability to do logic. Rather, they can isolate some of the actually important properties, avoid cognitive biases, etc.
Purely for example, humans (normally, etc.) have color vision, and that is the only reference to colors we have. However, that does not mean that human color vision is flawless. Under certain light conditions (low light, unusual lighting, etc.), humans can't see colors. But a sufficiently well tuned machine (even if ultimately based on the human color vision) could be much better than humans at detecting colors.

So, of course philosophers, etc., need the human logic ability to do logic. That does not mean that they can't avoid the pitfalls of it, or that they cannot shed light on important properties of it that most people do not see or do not care to see.

Also, there are colloquial terms of improper arguments - namely, 'improper', among others -, but colloquial language is not fine-grained. On the other hand, thinkers who have studied the rules of proper reasoning have more fine-grained terms that allow them both to isolate different properties of arguments and different sorts of errors - e.g., invalidity of a deductive argument is not the same as unsoundness, whereas non-deductive arguments are classified differently.

 

[Speakpigeon]

So, of course, I am not at all denying that humans (normally functioning ones at least) have a capability for logic, even if human intuitions on the matter are often flawed.

How often?

In fact, you just don't know what you're talking about. You are merely confusing logical intuition with something else. That's the flaw in your reasoning here. So, you're right, human reasoning is often flawed, yours is a good example, but that doesn't mean logical intuition is "often flawed".

In people in good heath, logical intuition is as good as their eyesight, something which is pretty good. 525 million years of evolution should guarantee us good logical intuition.

If you want to claim otherwise, please provide examples of flawed logical intuition.

A formal logic does not need to follow the flaws of the human ability to do logic. Rather, they can isolate some of the actually important properties, avoid cognitive biases, etc.

That's definitely what it should be doing but also definitely not what it is doing at the moment. Instead, formal logic is worse that our logical intuition.

Up until current mathematical logic was first conceived by Frege and Russell around 1900, formal logic was as good as our logical intuition. Arguably better since you can write very complex syllogisms which although easy to unpack for the logician would stump most people. So Aristotelian-style formal logic goes a little bit beyond our logical intuition. That was the idea of course and so it works.

Current mathematical logic isn't even logic since it can't do what our logical intuition does with syllogisms.

Purely for example, humans (normally, etc.) have color vision, and that is the only reference to colors we have. However, that does not mean that human color vision is flawless. Under certain light conditions (low light, unusual lighting, etc.), humans can't see colors. But a sufficiently well tuned machine (even if ultimately based on the human color vision) could be much better than humans at detecting colors.

Good example.

So, of course philosophers, etc., need the human logic ability to do logic. That does not mean that they can't avoid the pitfalls of it, or that they cannot shed light on important properties of it that most people do not see or do not care to see.

What pitfalls?! Mathematical logic can't even reproduce our logical intuition, let alone show any pitfall in it!

Also, there are colloquial terms of improper arguments - namely, 'improper', among others -, but colloquial language is not fine-grained. On the other hand, thinkers who have studied the rules of proper reasoning have more fine-grained terms that allow them both to isolate different properties of arguments and different sorts of errors - e.g., invalidity of a deductive argument is not the same as unsoundness, whereas non-deductive arguments are classified differently.

Thinkers haven't waited for Johnny-comes-lately mathematicians. Formal logic exists since 2,400 years and as such it works fine. Not so mathematical logic.

Mathematical logic is a joke.

Still, if you want to make yourself useful, here are the questions you need to answer:

How often is our logical intuition wrong?

What are your examples of flawed logical intuition?

What are the pitfalls of our logical intuition?

What is the justification given by mathematicians, logicians, philosophers etc. that would support your claim that the definition of logical validity you use is the correct one?
EB

 

[Angra Mainyu]

How often?

In fact, you just don't know what you're talking about. You are merely confusing logical intuition with something else. That's the flaw in your reasoning here. So, you're right, human reasoning is often flawed, yours is a good example, but that doesn't mean logical intuition is "often flawed".

That I do not know how often does not change the fact that I can observe it.

But it is often flawed. It is not just the reasoning done deliberately and consciously (if that is the distinction you want to make), when the person is aware she's doing it. There are cognitive shortcomings pretty common among humans (e.g., religion, other ideologies, political commitments) that damage their ability to reason in general, and their logical intuitions in particular. But moreover, logical reasoning - even done deliberately - is based on unconscious intuitions: If one is trying to prove something in mathematics, one deliberately thinks about different parts of the argument, but many things just come to one's mind as one does it. And that processing is subject to a number of flaws: even good mathematicians make mistakes and have to check and recheck and re-recheck their arguments.

Still, with training, our ability to do logic obviously improves.

Now, you might say that none of those errors are errors in the intuitions but in the reasoning. I would say that that's a terminological matter, but regardless, if you want to say that, then I would say modern logic is good for significantly reducing errors in logical reasoning (in addition to other things, like proving things one would not be able to prove otherwise due to lack of computational resources in the brain; it gives an easier method in many cases).

In people in good heath, logical intuition is as good as their eyesight, something which is pretty good. 525 million years of evolution should guarantee us good logical intuition.

Of course, human eyesight is also flawed in different ways. For example, there are a number of optical illusions regarding the size of objects. Also, the colors are not clear under different light conditions, etc. And apart from the fact that most of the brain machinery of humans evolved much more recently and did not involve 525 million years, that is beside the point too, in a way: in the ancestral environment, the human flawed sense of logic turned out to be good enough.

That's definitely what it should be doing but also definitely not what it is doing at the moment. Instead, formal logic is worse that our logical intuition.

No, formal logic is based on our intuitions of course, but isolating some of the bad parts and doing more finely-grained logic. Of course, mathematicians and logicians (and philosophers too) are overall much better at logic than the general population, and their intuitions are also much better - mental intuitions can be trained just as muscles and other thing can, and in these cases, they have been trained.

Up until current mathematical logic was first conceived by Frege and Russell around 1900, formal logic was as good as our logical intuition. Arguably better since you can write very complex syllogisms which although easy to unpack for the logician would stump most people. So Aristotelian-style formal logic goes a little bit beyond our logical intuition. That was the idea of course and so it works.

Well, Aristotelian logic was an improvement over untrained, wild intutions at least for most people, at least within its scope of application. But still, it does not work well enough. Bomb#20 already provided an example that you have yet failed to address: "Daisy is one of my farm animals. All my livestock are cows or horses. All cows have hooves. All horses have hooves. Therefore, Daisy has hooves."
Now, some people can make that inference intuitively, so in that context, Aristotelian logic was not an improvement. But still, some people are not able to make that inference intuitively. And yet, if they knew formal logic, they would have no problem (though if their trained their minds enough to understand formal logic, probably they would not even need it for something as easy as that!).
Moreover, there are plenty of inferences that are much more difficult that that one, including some that are beyond human comprehension without predicate calculus, but they are doable (by sufficiently smart and trained people, at least) in predicate calculus.

How often is our logical intuition wrong?

I do not know, but the logical intuition of people who are not mathematicians, logicians, etc., seems to be considerably flawed, as you can see for yourself by reading these and other threads, and generally the conclusions people reach or fail to reach. Now, part of that is the result of religion or non-religious ideology, but part of that seems to be simply that people are not sufficiently well trained for some pretty complicated arguments, even if their intuitions are good enough for daily life arguments, the ancestral environment, etc. (when it comes to ideology, etc., the flaws may well have been adaptive, as failing at logic but avoiding social shunning or worse as a result was probably good for reproduction, on average).

As for mathematicias, etc., well, the intuitions are generally better, but still, even in contexts not involving religion, other ideologies, etc., errors are pretty common (you can see that in mathematics too; one need to check, and check, and check, etc.).

What are your examples of flawed logical intuition?

Already given.

What are the pitfalls of our logical intuition?

I haven't found all of them!
But there are general tendencies to error in our reason, like committment to an ideology, cause, etc., which result in motivated reasoning (for example). Motivated reasoning might even play a role outside contexts like ideology and the like: for example, if one wants to prove a result, one may end up falsely believing one did. Was that because one wanted it? Or was the tendency to error independent of one's emotional investment? I do not know. But regardless, errors like that are common even in mathematics.

Now, again, you might say that none of those errors are errors in the intuitions but in the reasoning. I would say that that's a terminological matter, but regardless, if you want to say that, then I would say modern logic is good for avoiding errors in logical reasoning.

What is the justification given by mathematicians, logicians, philosophers etc. that would support your claim that the definition of logical validity you use is the correct one?

Your insistence on that is very irrational, as explained here(for example).

 

[Speakpigeon]

That I do not know how often

Exactly, you don't. You don't even know what we're talking about.

I would say modern logic is good for avoiding errors in logical reasoning.

How would you even know that?! You've as good as admitted you don't know that mathematical logic is correct! You're just being terminally incoherent.

Still, it's fun, you clearly don't understand much on this issue. You're the typical dogmatic senselessly regurgitating the dogma. You're your typical ignoramus believing he has some expertise.

What is the justification given by mathematicians, logicians, philosophers etc. that would support your claim that the definition of logical validity you use is the correct one?

Your insistence on that is very irrational, as explained here(for example).

So, you don't even understand such a simple question that you think you've answered it when you haven't!!!

You're just wasting my time.
EB

 

[fromderinside]

Wasting his time? But, he's the one responding. I believe he's wasting his time.

 

[untermensche]

To think you can separate truth from logic is stupidity.

If something is not true there is no logic in saying it is.

A premise that is not true is a waste of time.

 

[fast]

To think you can separate truth from logic is stupidity.

If something is not true there is no logic in saying it is.

A premise that is not true is a waste of time.

Why do you say things like that? Don’t counter examples just come flooding in?

 

[untermensche]

To think you can separate truth from logic is stupidity.

If something is not true there is no logic in saying it is.

A premise that is not true is a waste of time.

Why do you say things like that? Don’t counter examples just come flooding in?

I say things like that because I believe them.

Logic is not a game. Even if children like to use it for games.

Logic is a way to possibly arrive at truth. It is practical not frivolous.

 

[Speakpigeon]

To think you can separate truth from logic is stupidity.

If something is not true there is no logic in saying it is.

A premise that is not true is a waste of time.

Why do you say things like that? Don’t counter examples just come flooding in?

I say things like that because I believe them.

Logic is not a game. Even if children like to use it for games.

Logic is a way to possibly arrive at truth. It is practical not frivolous.

So, what's your preferred method of formal logic?
EB

 

[fast]

I say things like that because I believe them.

Logic is not a game. Even if children like to use it for games.

Logic is a way to possibly arrive at truth. It is practical not frivolous.

So, what's your preferred method of formal logic?
EB

The word “formal” has no impact on his understanding. That is just elitist masturbation in his mind.

 

[untermensche]

Why don't you think truth matters?

What is logical about assuming something clearly false is a valid premise?

 

[fast]

Why don't you think truth matters?

What is logical about assuming something clearly false is a valid premise?

The truth matters. I am not of the mind that it doesn’t.

If I say that an argument is valid and you say that a premise is valid, we are not using “valid” the same way.

 

[untermensche]

I am saying that without valid premises the form of the argument is meaningless.

 

[ruby sparks]

What is a valid premise? I'm not even sure there is such a thing in logic?

 

[untermensche]

We're talking about truth.

A valid premise is just a premise that is not clearly false or known to be false.

If your premises are not valid any argument made from them is worthless.

Where the idea that accepting false premises is logical came from is beyond me.

 

[Speakpigeon]

Why don't you think truth matters?

What is logical about assuming something clearly false is a valid premise?

The truth matters. I am not of the mind that it doesn’t.

If I say that an argument is valid and you say that a premise is valid, we are not using “valid” the same way.

Valid
1. sound; just; well-founded.
2. producing the desired result; effective: a valid remedy.
3. having force, weight, or cogency; authoritative.
4. legally sound, effective, or binding: a valid contract.
5. (of an argument) so constructed that if the premises are jointly asserted, the conclusion cannot be denied without contradiction.
6. Archaic. robust; healthy.

EB

- - - Updated - - -

What is a valid premise? I'm not even sure there is such a thing in logic?

Valid
1. sound; just; well-founded.
2. producing the desired result; effective: a valid remedy.
3. having force, weight, or cogency; authoritative.
4. legally sound, effective, or binding: a valid contract.
5. (of an argument) so constructed that if the premises are jointly asserted, the conclusion cannot be denied without contradiction.
6. Archaic. robust; healthy.

You're not trying.
EB

 

[untermensche]

If something is false it most definitely is not well founded.

You have a narrow vision.

 

[fast]

What is a valid premise? I'm not even sure there is such a thing in logic?

In technical usage, there is no such thing as a Valid Premise. “Valid” is a term that applies solely to deductive arguments.

If someone imports common usage and tries to apply it on the convention we regard as technical, all kinds of ambiguity arises.

 

[untermensche]

A valid premise is a truthful premise just like a valid excuse is a truthful excuse.

Would you call something that was a clear lie a valid excuse?