if we're loose about what we mean by "certain" and don't mean "exactly 100% certain" then totally.

But if certain means perfectly 100% certain, no room for error, then it just seems immensely easy to think of things that could go wrong. One of my ex girlfriends had her middle name misspelled in her certificate - swapped a g for a j. If that's capable of happening, I find it very easy to imagine someone writing in a wrong date, swapping a 6 for a 5 perhaps.

And that's not even getting into the conspiratorial stuff.

If you feel certain, all the power to you. I just don't think so. I don't think it's fair to say, about this sort of thing, "there's absolutely no way anything on my birth certificate could be incorrect".

Here's what the real modus ponens looks like in the checker

https://www.umsu.de/trees/#((p~5q)~1p)~5q

That's affirming the Antecedent, which is how modus ponens really works.

Then we modify it to your denying the Antecedent variation

https://www.umsu.de/trees/#((p~5q)~1~3p)~5~3q

Invalid

If you want to use the logic checker correctly, here's how you do it. First I will demonstrate a valid argument, Modus Tollens

https://www.umsu.de/trees/#(p~5q)~5(~3q~5~3p)

Then, if we slightly modify it to your argument, which is that if you have p implies q, you can get not p implies not q, look at what happens

https://www.umsu.de/trees/#(p~5q)~5(~3p~5~3q)

Modus Tollens is a valid argument format. It is generalisable and applicable to any p implies q situation.

Denying the Antecedent is invalid. It is not generally true, it is not applicable to all p implies q situations. It is trivially easy for anybody to think of situations where it doesn't apply.

You have chickened out of every disagreement once it's starts looking like you might be wrong. Be brave. Look at the possibility that you might be wrong in the face. I dare you.

Almost none of what you said is pertinent to any conversations being had here. Not the "I think therefore I am" conversation. Not the "is denying the Antecedent a logical fallacy?" conversation.

"I think therefore I am" is not meant to be applied to someone else, it's meant to be applied to yourself only. Every person can only apply it to themselves.

You aren't using the logic checker correctly. You've misunderstood what v means.

if that were true, then this:

(p→q) ∨ (¬p→q) is valid.

Shows that "Not P then Q" is validly drawn from P →Q.

I'm using the same reasoning as you.

The thing you're getting confused by is thinking v can mean "the right side is validly drawn from the left side". That's not what v means.

so are you agreeing that "(p→q)∨(¬p→¬q) is valid according to this logic checker" doesn't prove anything?

If not, what do you think it proves?

What does "(p→q)∨(¬p→¬q) is valid according to this logic checker" prove in the context of this conversation?

But the logic checker says it is valid. — Corvus

You haven't quite grokked what the logic checker is actually doing. Guess what else the logic checker says is valid:

(p→q) ∨ (¬p→q) is valid.

Also

(p→q) ∨ (p→¬q) is valid.

I agree too. — Fire Ologist

Do you agree with him for the same reasons he thinks?

He thinks that if someone accepts "I think therefore I am", they must also accept "I don't think, therefore I am not". In other words, and in his own words:

P-> Q
Not P
Then it must be Not Q

Is this good reasoning?

I don't really know what you mean by this. Something? There must be something?

How can you be 100% certain of your place of birth? You can't imagine any circumstance where that's a lie? You probably don't remember it yourself. You're trusting other people to be telling you the truth, how are you 100% certain?

"Identical" is a strange wording that's prone to confusion due to different people's understanding of what that exactly entails. That's why most philosophers talk in terms of supervenience instead.

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

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

"no matter what" - can you really say that? You have the thing to convince me, your textbook, and you said you'd post pictures of it. You haven't done that, so until you do that, there's no way to say "no matter what".

I don't think agreeing to disagree makes sense here, because it's simple logic. It's not opinion. It's not even obscure knowledge. It's easily demonstrable. One of us is right and one of us is wrong. If we can't come to an agreement on this, then one of us is truly intellectually hopeless.

I think your insistence on agreeing to disagree is a pretty big sign that you know you're wrong. If I say 2+2=4, and you say 2+2=5, then of course you're going to propose to agree to disagree. I don't have any need to do that, because I can demonstrate the validity of my idea. Only the guy saying 2+2=5 is motivated to agree to disagree, because proof of hopeless for him.

I know you've looked in your books

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.

so how can you tell the difference between someone willing to accept truths and someone unwilling?

I mean, we're all wrong about some things, right? So "someone willing to accept truths" means someone who can describe to you the conditions for changing their mind, for accepting that they were wrong.

I have laid out the conditions for changing my mind - show me the pages from the textbooks. What conditions do you have that could demonstrate to you that you're wrong? What would convince you?

We know it's not concrete logical examples, Oxford university, Stanford university, or other people systematically disagreeing with you here in the forum. So what could it be?

If you can't be convinced you're wrong about this, I don't think you can be convinced you're wrong about anything.

Another point that you must note is that, Logic is not an effective tool for those folks who are psychologically motivated to push their own ideas to other folks.  For them logical arguments and proofs would mean nothing for changing their biased views on certain ideas they wanted to push to other folks.  They won't accept logical truths as truths.  They will keep denying verified and proved truths as fallacies.

Reasonings and Logical proofs are only effective for those folks who are authentic and willing to accept truths as truths. — Corvus

Fully agreed

Even when we DO have a unified language we can't find universal agreement.

https://thephilosophyforum.com/discussion/comment/889798

We have a unified language here - basic symbolic logic - and entire books worth of agreed-upon usages of that unified language, and yet you still get people explicitly misusing it while being completely and entirely unwilling to consider the possibility that they're misusing it.

I'm not saying unified languages are not useful, they're just not a panacea. They can't help everybody.

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.

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?

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.

You should get some sleep. Your nonsense is degrading to worse than usual. Maybe tomorrow you'll be ready to drop the fallacies.

what in the world are you talking about?

If I'm holding a flower, I'm holding a plant.
I'm not holding a flower.
Therefore I'm not holding a plant.

Does that argument make sense to you? It doesn't make sense to me. There are a hell of a lot of plants that aren't flowers that I could be holding.

If my pet is a mouse, then my pet is a mammal.
My pet is not a mouse.
Therefore my pet is not a mammal.

Good argument, you think?

This is implied from P logically oK?? — Corvus

No, not okay. It's the same Fallacy. Why are you insisting on the same Fallacy when you know it's not in your textbook? When you know Stanford university and Oxford university are explicitly calling it a Fallacy?

You've failed to find it in your book, and yet you're still presenting the argument like it's valid. Grow some balls and admit your mistake please. Denying the Antecedent is a Fallacy.

Please tell me what is the point you don't see in my post above — Corvus

The part where you're continuing to apply the exact same argument, which you erroneously call modus ponens, even though you know it's a fallacy.

P = I think, therefore I exist.
Q = I don't think, therefore I don't exist.

P - > Q

Here.

You have the textbooks. You keep presenting this argument, but you aren't presenting the pictures. Put your money where your mouth is. If you can't produce the pictures, this argument is just a fallacy. It's called Denying the Antecedent, you have all the resources you need to understand why it's a Fallacy, and you haven't provided any resources to defend the position that it's not a Fallacy.

You have one job. The pictures. You can win the argument if the textbook says what you insisted it says. There's really no point talking about anything else, until you produce the pictures. Are you brave enough?

you introduced your modified "modus ponens" all on your own. Despite your failure to find any supporting pages, you're STILL using your own fallacious version of "modus ponens" in your recent posts.

I'm not making it complicated, I'm making it simple. The Fallacy of denying the Antecedent is exceptionally simple. By focusing on this, I'm simplifying the conversation.

You said earlier that it could be found in any logic textbook. You apparently have multiple logic textbooks, and you can't find it in one.

It's time for you to stop deceiving yourself.

Here's a modus Tollens for you:

If it's true that you could find it in any logic textbook, you would be able to find it in your logic textbooks.
You can't find it in your logic textbooks.
Therefore, it's not true that you can find it in any logic textbook.

That's what valid logic looks like.

Mad props for telling the truth, that you looked and can't find it. I respect that, and did not expect it.

Do you think it's possible that it's not a coincidence that I predicted you would not find your argument supported in your logic books?

Usually not realistic, that's why there are bugs.

How is it possible for the rules that describe a game to be wrong? — Ludwig V

Because the people implementing them didn't think about all the cases. There are usually edge cases they didn't think of, or interactions between features they didn't plan for.

If I don't, then you know the answer. — Corvus

Is this you confirming that you won't post the pictures if they don't confirm your beliefs? I truly hope that you can be better than that

If you say, you think therefore you are, is the only way for you exist, then when you are not thinking, you stop existing. That is what you mean logically. Don't you find that absurd? — Corvus

Please save this argument for after you post the pictures from your textbook. Your argument will hold more weight then - or it will disintegrate, depending on what's in the book.

There is. Post the textbook. I've literally described to you the exact thing you can do to change my belief. Show where in your textbook Modus Ponens is

P --> Q
¬P
=====
¬Q

You are copping out out of fear. Let go of your fear.

If you had true intellectual courage, you'd pledge to go and post the pictures from the textbook about Modus Ponens no matter what the textbook says. Even if it agrees with me. I would love to see you have that kind of courage.

You have the proof, you have the very thing that could either change my mind, or maybe, if you have any balls, change your mind. We don't have to agree to disagree, because you literally have the proof.

We don't have to agree to disagree. You have a textbook. I like textbooks. I trust textbooks. If you are correct, you can convince me.

That's my strength - I can be convinced by things.

If I'm correct, can I convince you? I'm a lot less sure of that.

I love to be corrected. Your textbook photographs would correct me. You love to correct people - you've been arguing for pages that I'm wrong, so you must want to correct me.

If I love to be corrected, and you love correcting people, then let's both get what we want by you posting the pictures from your textbook. It's a win-win. I'd love to see you win in this way.

"Agree to disagree" just sounds like another way of wording "I looked in my textbook and couldn't find what I said was going to be there". So... if that's where this ends, then I'll know you looked and didn't find it.

I feel like this is a really sad way of admitting that you looked through your logic books and can't find any indication that Modus Ponens does what you say it does. Is that what this is? Please be honest.

If I had the proof you say you have, and I had a willing listener like you have, willing to look at that proof, I'd just... post it. I'd post the picture of the textbook.

And if I looked in my textbook and found no proof of my belief, and I had too much pride because I'd dug myself into too deep of a hole by being so relentlessly condescending (which, if you look in the conversation history, you will see that you started with the condescension, and not me) - if I looked in my textbook and found no proof, I would post exactly what you just posted. "There's no point talking anymore." That's exactly what I'd post if I was too proud to admit I'm wrong.

So either you post the picture from your textbook, or I know that you're too proud to admit that you can't find it.

Unlike you, I'm actually willling to look at sources other people provide for their arguments. You won't look at my sources, fine, let's look at yours. Post pictures. I'm not too cowardly to look at your sources. Let's see em.

You're right, just pictures. You said you would post pictures. Don't waste time, post pictures.

All this talk and no pictures.

Would you like to make a bet?

P --> Q
¬P
=====
¬Q

I want to bet that you won't find a single textbook that will affirm that this is a valid argument. I want to bet that when you look up Modus Ponens, you will get

P --> Q
P
=====
Q

You might also be able to find Modus Tollens

P --> Q
¬Q
=====
¬P

But not a single textbook of yours will confirm the top argument. They may present the top argument as a fallacy, but not as a valid argument.

I think the terms of the bet should be intellectual humiliation. What do you say? Bet?