Obviously your syntactic confusion has been adding to the whole mix up. Good night.

I robbed a bank, therefore I committed a crime.
I did not rob a bank, therefore I did not commit a crime

argues the man accused of rape
after the video of him raping the victim is shown

Of course, there can be situations where denying the antecedent can also be true. But if it is presented as a logical necessity, it doesn't hold. It's not enough. Throw in an if and only if, and it can work, but that's a different condition.

Lots of fodder for thought here!

What can we know for certain? IMHO there is a threshold that you reach or don’t.

Either you are forever ensconced in solipsism, or you accept the world and everything in it

Any secondary knowledge after the first acceptance is almost a semantic difference.

Epistemologically speaking, the answer is that certainty is a myth, but what we call certainty is fairly common. I run a software company. It’s analogous to what my c++ instructor once said a long time ago: “ There are two kinds of programmers. One kind makes relatively simple programs. The other kind makes programs with bugs in them. I want to teach you to make programs with bugs in them. “

Aka: there are two types of certainty: the tautological kind, and the kind that has flaws. And it is better to have the kind that has flaws.

Three people in here who think it's a fallacy, only you who can't find it in your book thinks it's not. I have linked documents from Stanford and Oxford that say it's a Fallacy.

Is the entire world crazy and only you are correct? Or is it more likely that you are incorrect?

Here's a guy online with the same confusion as you

https://philosophy.stackexchange.com/questions/46651/question-about-validity-of-modus-tollens-vs-denying-the-antecedent

Big difference is, if you look, he answered his own question about the Fallacy, and he corrected himself.

Why is it that the one person I find online who shares your belief only shared it temporarily, until he thought about it for a minute and came up with intuitive counter examples? Why did the only guy to share your belief quickly come to share my belief? The belief I share with so far every other person on this forum who has weighed in, and Stanford, and Oxford?

Why can't you find it in your book?

If you aren't seriously considering the possibility that you're wrong at this point, you've got to be trolling.

I thought our discussion had been over about 10 pages ago. You kept on hounding me with the same daft questions and irrelevant comments for some reason. It just seems to me some obsessive troll you are after. Nothing more to add, and nothing more to discuss with you for this particular topic, afraid. Bye.

it's not irrelevant because you keep using the same Fallacy. "Nothing more to discuss with you" is a funny way of saying "I looked in my books and couldn't find it".

You aren't being honest or honourable here. Are you trolling?

You thought the conversation was over 10 pages ago, but 10 pages ago there's no pictures of the textbook. Did you agree you're incorrect 10 pages ago?

Of course, there can be situations where denying the antecedent can also be true. But if it is presented as a logical necessity, it doesn't hold. It's not enough. Throw in an if and only if, and it can work, but that's a different condition. — Bylaw

Good point. I am not going to deny your point straight away. I wouldn't be that rude.
But it seems that you talking about again totally different case in your example. Why it is irrelevant, if you want know, then let me know.

I looked at one of my old textbook called "Discrete Mathematics" by P Bogart.
It says, P --> Q is equal to ¬P V Q.
This makes sense, and seems to prove my logic was correct.
I think therefore I am is unsound.

This makes sense, and seems to prove my logic was correct. — Corvus

That in no way proves your logic is correct. notP still does not necessitate notQ.

What do you mean "good point"? You've just disregarded what he said.

Good point. I am not going to deny your point straight away. I wouldn't be that rude.
But it seems that you talking about again totally different case in your example. Why it is irrelevant, if you want know, then let me know. — Corvus

OK, I was under the impression you were arguing with only the general rule. IOW using a general rule that shows the cogito is false. I don't think it's a good rule, for reasons/examples given by others. But here you say it is a different case. Well, then it doesn't like a rule is being used.

In that case it is not the rule the is running the argument but something more complicated.

IOW if I look at many of your posts it seems like you are saying the rule shows that it's false. But the moment you indicate that it works 'in this case' (but not in others), it seems to me, this is directly acknowledgement that it's not the rule. It's a specific situation or a specific condition, for example the 'if and only if case' special condition.

And, hey, post a picture of the textbooks. If it's there, that will surprise people and might move things forward.

Oh, and this isn't because I buy or like the cogito. I actually don't.

It says, P --> Q is equal to ¬P V Q. — Corvus

I think → I am. P is "I think" and Q is "I am".
P – Q – ¬P∨Q (aka P→Q)
0 – 0 – 1 "I don't think and I am not" holds P → Q
1 – 0 – 0 "I think and I am not" does not hold P → Q
0 – 1 – 1 "I don't think and I am" holds P → Q
1 – 1 – 1 "I think and I am" holds P→Q

OK, I was under the impression you were arguing with only the general rule. IOW positing a general rule that generally is considered false and the examples I and others have given, I think show it's not a good rule. — Bylaw

Yes, but your example and the other's examples are the case of categorical mistake. This is the problem with the symbolic classical logic. Because it uses variables instead of the real objects and cases in the world, they think they can use any irrelevant items and cases into the variables, which looks like the general rules doesn't make sense. That is why sometimes you must investigate the content in the propositions to see if they make sense.

But your point is good in that it reveals the problems with the misuse of the logic.

Your example, bank robbery has nothing to do with rape the criminal committed. They are totally separate matter. And yet, the criminal was trying to distort the truth as if they were the same category of crimes. They are different category of crimes. It is like saying

Socrates is a man, therefore he is mortal.
A dog is not a man, therefore he is immortal.

You swapped over Socrates with a dog. That is illegal in logical arguments.

And, hey, post a picture of the textbooks. If it's there, that will surprise people and might move things forward. — Bylaw

I am no longer communicating with the folks who appear to be psychologically biased on this topic.

Oh, and this isn't because I buy or like the cogito. I actually don't. — Bylaw

That's cool. :up:

Wanting to see the pictures of the textbook is psychological bias . This is too fucking funny.

I can just picture it. He's sat in his room, flipping through the textbooks, desperate to confirm his beliefs. First textbook, nope, no sign of it. Second textbook, nope, no sign of it. He clenches his fist. One more textbook to look through. And... nope, no sign of it. No text in his textbooks indicates that it's valid to deny the Antecedent.

But it's too late now, I can't give fj the satisfaction. I know, I'll pretend like I'm too good to look at a textbook, even though it was my idea in the first place. I'll even try to make it seem like people who are interested in the textbook are disingenuous! That's my out!

I mean, either that's the story, or corvus has been trolling the whole time. He's a pretty good troll if that's what he's been up to.

0 – 0 – 1 "I don't think and I am not" holds P → Q — Lionino

I don't think and I am not is FALSE.
so P -> Q is false at that point.

What's the Las Vegas on corvus actually believing what he's saying?

I don't think and I am not is FALSE.
so P -> Q is false at that point. — Corvus

:rofl: :rofl: :rofl: :rofl: So you are disagreeing with P Bogart, who you yourself quoted. That's crazy.

:rofl: :rofl: :rofl: So you are disagreeing with P Bogart, who you yourself quoted. That's crazy. — Lionino

This is exactly the point I was making with misuse of Logic. P Bogart is not a math god. He is just a math teacher.

At Not P --> Not Q, if you were sensible, you would have inspected the content, which was FALSE.
Because it is FALSE the assumption, P->Q must be FALSE. You are guilty of the misuse of Logic.

You seem to be naively following the symbols as if they were some message from God.
You must inspect the contents of the symbols to decide for truth values as you keep progressing your reasoning and inferencing mate.

IOW if I look at many of your posts it seems like you are saying the rule shows that it's false. But the moment you indicate that it works 'in this case' (but not in others), it seems to me, this is directly acknowledgement that it's not the rule. It's a specific situation or a specific condition, for example the 'if and only if case' special condition. — Bylaw

But rules are for us to apply them into the individual cases. Rules don't exist just for rules themselves, or for its own sake of just existing as rules. When you are going through the rules inspecting the corresponding real life cases, you can see the truth or false values by comparing them with the reality in the world, or the state of objects or situations.

Having said that, I agree with your point, that this particular case would have done with more stringent conditionals on the premise and also the assumptions.

The bottom line is that, Logic is not the core problem here. Logic was introduced to help clarifying the main point Cogito. Unfortunately it didn't seem to help much in doing so. As I said in the other thread, sometimes psychological bias seem to override logical arguments.

Cogito could have been not a statement that can be proved logically first place. Because it was never a logical statement. So, if we agree that Cogito is an epistemological issue, then it still is absurd to say Cogito necessitates existence. It would be rather perception, memories, imagination and sensations as well as reasoning and all the rest of the total mentality which grant one's own existence, I believe.

P Bogart is not a math god. He is just a math teacher. — Corvus

So why did you even quote him?

At Not P --> Not Q, if you were sensible, you would have inspected the content, which was FALSE.
Because it is FALSE the assumption, P->Q must be FALSE. You are guilty of the misuse of Logic. — Corvus

This makes no sense. It is not a coherent thought.

Previously you were arguing that P→Q implies ¬P → ¬Q. That was your argument that the cogito is logically incoherent. The issue is that P→Q is completely unrelated to ¬P→¬Q.
https://www.umsu.de/trees/#(p~5q)~4(~3p~5~3q)
https://www.umsu.de/trees/#(p~5q)~5(~3p~5~3q)
https://www.umsu.de/trees/#(~3p~5~3q)~5(p~5q)

It would be rather perception, memories, imagination and sensations as well as reasoning and all the rest of the total mentality which grant one's own existence, I believe. — Corvus

Oh hell nah @flannel jesus

Yeah he's just kinda flailing about at this point, not saying a whole lot (and certainly not providing any pictures from textbooks)

So why did you even quote him? — Lionino

To get some ideas. Did you think I quoted him because he was a god? blimey :roll:

This makes no sense. It is not a coherent thought. — Lionino

Could it be a psychological block somewhere in the thought?

It would be rather perception, memories, imagination and sensations as well as reasoning and all the rest of the total mentality which grant one's own existence, I believe. — Corvus

Cool, this exactly Descartes' argument, but put more poorly.

Thanks for wasting everybody's time.

Yes, but your example and the other's examples are the case of categorical mistake. This is the problem with the symbolic classical logic. Because it uses variables instead of the real objects and cases in the world, they think they can use any irrelevant items and cases into the variables, which looks like the general rules doesn't make sense. That is why sometimes you must investigate the content in the propositions to see if they make sense. — Corvus

That's fine, but then both sides of the use of denying the antecedent here are arguing using symbolic logic. If we need to look at the individual case, then we can skip either use of the the rule (the symbolic logic) and just make the case focused on individual qualities and categories.

Maybe this was done earlier in the discussion and I missed it, but it would seem to me that your argument here would be that both sides stop using symbolic logic.

Having said that, I agree with your point, that this particular case would have done with more stringent conditionals on the premise and also the assumptions. — Corvus

Or, yes, one could do that.

Cogito could have been not a statement that can be proved logically first place. Because it was never a logical statement. So, if we agree that Cogito is an epistemological issue, then it still is absurd to say Cogito necessitates existence. It would be rather perception, memories, imagination and sensations as well as reasoning and all the rest of the total mentality which grant one's own existence, I believe. — Corvus

It does matter what the Cogito is trying to demonstrate. I think 'experiencing is happening, something exists' is less troublesome, though it's almost redundant: what is before the comma is a paraphrase of what is after the comma.

Cool, this exactly Descartes' argument, but put more poorly. — Lionino

Descartes said "He thinks, therefore he is." What are you talking about?
Thinking is not totality of mind. Thinking also has objects and contents. Descartes didn't even specify what they were. Hence it wasn't even a logical statement. As you admitted before, it was an inference.

Thanks for wasting everybody's time. — Lionino

I have been only trying to reply to your questions and posts.
Everything you say seems not reflecting the reality or facts.

Thank you for your reply. I agree.

There are two kinds of programmers. One kind makes relatively simple programs. The other kind makes programs with bugs in them. I want to teach you to make programs with bugs in them. “

Aka: there are two types of certainty: the tautological kind, and the kind that has flaws. And it is better to have the kind that has flaws. — Metaphyzik

Love it.

The tautological kind shows us what certainty is, but gives us no real content. The simple non-buggy program we build is perfect example of certainty, but the program does no real work.

When we build complex things to do real work, we can take our understanding of the certain learned from the tautologous kind, and keep it as a tool to inspire improvement or identify areas that need to be tested to further the goal of getting some real work done as we build, but this is now a use of certainty in the process of building without a goal of achieving certainty in the function of the program, just the goal of getting the work done.

All of this means to me three things: we know tautologous things for certain; so we know what certainty is for certain; and we will rarely see certainty outside of tautology but nevertheless can use it as a guide to getting work done.

I think we know trillions of things with certainty. For example, I know that the English word "sky" is spelt "sky".

You haven't understood the issue of skepticism: https://plato.stanford.edu/entries/skepticism/

For example, I know that the English word "sky" is spelt "sky". — Truth Seeker

That looks like an example of a tautologous kind of certainty.

How does knowing trillions of things with certainty respond to what I said? Can’t tell whether you saw what I was trying to say or not. Are you adding to it, narrowing it, disputing it, agreeing with it?

Good points.

I am suffering from depression and CPTSD so reading is hard. Understanding abstruse philosophical articles is impossible in my current mental state.