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.

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.

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

what in the world are you talking about? — flannel jesus

You are totally ignoring the plant you were talking about in the proposition, and suddenly starting to making random inference of holding some other plant. Do you not even know what you were talking about?

But you are not holding the plant. You could be holding a plant.
You are not even able to difference between "a" and "the".

I haven't failed to find the book. I didn't even try to look at any book.

P->Q then
Not P -> Not Q

Why is this fallacy?

As I made clear already I am not going to flick through a Logic book to whatever ... no. There are more important thing to do in life.

If you cannot see my point in the written expressions, then there is no point I am afraid.

P: I think therefore I am. (This is the one you want to prove correct or not).
Q: I don't think therefore I am not. (This is implied from P logically oK???)
So, P ---> Q

But you know Not Q
Therefore Not P

It is so clear, what is it that you can't see ?

It is not MP or MT which is important here. They are just tools.
You seem to making out as if MP MT are some end point human race must achieve.

The core problem is to prove or disprove "Cogito Ergo Sum." is logically sound.
For that, normally folks wouldn't even need any Logic.

I only introduced the simplest Logic because you seem to be having difficulty in understanding anything on proving. But for some reason, you seem to be excited and obsessed with the definition of MP.

Well, if you cannot even understand what the core problem is about, what is the point of you learning about MP or MT or the rest of Logic? Please tell me what is the point you don't see in my post above, and I will try to explain it to you again if it looks any worthwhile.

Nope. You are wrong in your unfounded presumption again. I am not going to take out my logic books on my relaxing weekend time, just to prove what is self evidently true.

The explanation above in my post above is clear enough for this simple point for anyone to understand what it means. I hinted you to read some proper textbooks instead of keep getting confused based on ChatGPT's nonsensical info.

The core problem we were trying to prove is so simple and clear. Why do you try to make it complicated introducing the irrelevant points into it?

Post the pictures — Lionino

I cannot find the page relevant to this point in my logic books. I came home, sat down at the desk, and reviewed the whole point again. I still feel that Cogito Ergo Sum seems logically not sound.

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

P - > Q
Not Q (Q is FALSE)
therefore Not P (P is FALSE)

One's own existence is known by perception and sensation rather than just thought, no? Surely you must keep existing even when not thinking. Is this is the case, then I think therefore I am is not logically sound.

Holy shit. Obviously nobody said that. That doesn't even make sense. "I think therefore I am" is an inference. How can an inference be the only way for something to exist? — Lionino

Exactly :nerd: No wonder it didn't sound tightly logical necessity.

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 — flannel jesus

I am trying to focus on the discussion with without getting interrupted by the unusual requests and irrelevant posts.

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. — flannel jesus

Sorry but I am discussing this point with . Will get back to you after our discussion, if there is any more point for us to discuss on this particular point. If I don't, then you know the answer.

No it doesn't prove that. Your next move is to say "Why not". Because burden of proof is not on me. — Lionino

I don't think you showed any arguments for it doesn't prove that, did you?

Obviously, because you can't recall what you said 1 page ago, you will say those two are different. But: — Lionino

Classic symbolic logic works by showing how the arguments transit from one to the other mainly using the variables. Sometimes you would introduce negations, AND, OR connectives in the process of proving. But in the process, if you noticed the critical point where it disproves the core points, then it will deduce the conclusion from the statement which is obviously true or false. This is the way the logical proving works. You seem to be totally ignorant of how the proving procedure works. It is like those folks who are into the habitual copying and pasting truth tables and some symbols in the internet, and insist that is the only way MP works what have you.

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?
Do you stop existing, when you are asleep, or watching movies or listening to the music with no thoughts?

How about the walls in your room. The wall don't think. Does it mean they don't exist?

Please also understand the core problem here was proving whether "I think therefore I am." is logically correct. All the rest was just introduced as a process for the proof.
Your insisting on requesting photographic evidence of the textbook ... etc, sounds very bizarre to me.

If you can't see the simplest logical proof shown to you with the explanation for the point, then that is fair enough. There is really nothing anyone can do about that to change your belief.

No, it is nothing to be sad about. People disagree in the real world, and you must learn to accept it.

We agree to disagree on the point, and that is fine by me. I really do hope to see you understanding the points though. But if not, so be it.

I have given you the full proof using both symbolic logic and ordinary language. If you can't see it, then that is fine. I don't feel there is a point for any more discussion here on this particular point.

I don't think it needs any more time wasting mate.

You have admitted that When you don't think, you don't exist is incorrect.
That proves, When you think, you exist is also logically incorrect.
We didn't even have to go into the symbolic logic.
Why is it so hard to see it?

All I can say is, if you are that bothered with something, please read my post again for proving why "Cogito ergo sum" is logically incorrect.

You obviously don't even understand what the core problem is. The core problem is proving "Cogito ergo sum" is correct or incorrect.

It shows you are also one of the copy-paste internet info brigade without even knowing what it is, but not even knowing what we are trying to prove here.

Except for Stanford University and Oxford University, for starters. — flannel jesus

Now it gives me an impression FJ is a robot machine set up for keep replying automatically without even knowing what it is talking about. :roll: :chin:

You think therefore you exist? -> T (Assumption)
P -> Q = T (assumption)

When you stopped thinking, you don't exist? (jesus has admitted it is incorrect) -> F
Not P > Not Q  => F
T F -> F
P -> Q = F
Therefore you think therefore you exist is FALSE.

Please note T F are truth values of the propositions.They are not  propositions themselves.
Well, this is the last time I am trying to make you understand.  If you still can't, then I don't think there is hope.   It is shocking that 3 of yous are all in the same cave of confusion.  No one seems to be able to dig yous out the cave.

I shall give a try as per time permits.

Please remember. The classic symbolic logic works on the forms only. No contents. I have several Logic books at home. And they all say the same thing. You must get any symbolic logic books, and have a look into them. It will all be there.

This is the simplest logic. There is nothing much to it. Why you cannot see my point is beyond common sense.

It gives me impression that if you were found that your point was wrong, then you seem to be reverting back to ad hominem, or you haven't read what I said replies. That is why I feel that you and your pal the wonderer are inauthentic.

OK we had enough discussions on it. I will leave you to it. Good luck.

In symbolic classic logic, the contents don't matter. It works purely on the format.
So if you say,
P-> Q
Not P
Then it must be Not Q

There is no way Not P, and it is still Q.

The proof process goes on with introducing negations, assertions and inferences. That's why it could have Not P for the negation introduction. If Not P, then it must be Not Q.

But Not Q doesn't make sense. You confirmed that it is incorrect. Hence P->Q is incorrect.

You think, but sometimes you stop thinking. But you still keep existing.
Not thinking doesn't make you non-existence. You think therefore you are. is logically incorrect.

I hope this helps.

Sure, present your argument against it, if you have any. I must go and do some work. I will read it later.

Well, if you say it is incorrect, then you proved yourself, you think therefore you exist is incorrect too. That is a simple logic.

No it is not. You don't agree with that, is psychological. It is incorrect is factual.

Is it correct or incorrect?

Why do you refuse to answer to a simple question?
You don't think, therefore you don't exist. ==> Is this correct?

Because you couldn't understand the most basic demo of logic, I had to ask you in ordinary language about the point. You change the subject, and refuse to answer.
So, the only conclusion I can have is that, you are not an authentic interlocutor. Please read some books on the topic before engaging in the discussions.

You still refuse to answer. You are not an authentic interlocutor.

Don't change the subject. Please answer me.
You don't think, therefore you don't exist?

Obviously you have not read a single Logic book, but are copying and pasting some internet info here. So I shall not try with logic. In simplest ordinary language, If you don't think, you don't exist? You don't think, therefore you are not?

You can use MP using negation too. Please read some introduction to Logic.

What is there to misunderstand? It is the simplest symbolic classic logic. Only thing is your trying to distort the truth even I have shown the clearest logical proof.
It seems that even the simplest logical demo is not getting through to you. Only thing I could ask you is keep reading my posts, and think clearly until you can understand it.

Are you prepared to listen to find out why? — flannel jesus

Sorry. I have already explained in most clear logical way with even the simplest symbolic logic Modus Ponens demo example. If you still cannot see it, then I can no longer do any further. I shall not waste any more of your time or mine with this point. Have a good weekend jesus.

You really should stop. — Lionino

Just been pointing out the problems. :nerd: