Does this make sense? I am just checking. Please do point out if I have made a mistake somewhere. — Beverley

Yeah you are still right. Folks seem to think still I think therefore I am is some sort of logical statement, hence all the confusions.

Because they are so confused, we were trying to show in simple classic formal logic to see whats happening there.

In the course of logical proof, regardless of being invalid or valid, we can reason by introducing contradiction to the statement, and try to eliminate or trigger truth or falsity values from the statement. At this stage every statement is assumption. Contradiction reasoning is based on the identity principle that P = P, Q = Q. Therefore if P-> Q, then Not P -> Not Q must hold. This principle is priority to being valid or invalid of the assumptions.

When we examine Not P -> Not Q, we find that statement is incorrect. Hence P -> Q cannot be true.

This has nothing to do with Not P -> Not Q is a logical leap and all that nonsense.

Cogito is a subjective intuition. No one can inspect others' cogito apart from his / her own. Hence it is not an objective concept. It shouldn't have been even started for logical process.

But you are again correct. Because Cogito is an intuition, logical proof is impossible. It can only prove that it doesn't make sense concept, hence the statement Cogito ergo sum is false.

Hallelujah! I was doubting myself for a moment! I am not going mad then :) — Beverley

No you are not. Your reasoning and understanding are spot on.

The inference is invalid. logic does not show that if 'I think therefore I am' is true, then 'I do not think, therefore I do not exist' must also be true. — Banno

In the course of the proof, they are both assumptions until "I don't exist" is found False, when we checked it against the fact of human life in the world.

I just wanted to check, is your argument here that if 'I think therefore I am' is true, then logic dictates that 'I do not think, therefore I do not exist' must also be true. But since the latter makes no sense, then something is terribly wrong with it all?? Or am I totally wrong to assume that? I could have misunderstood. — Beverley

Yes, correct. You have got it spot on.

'I think therefore I am' implies 'I do not think, therefore I do not exist'. It is logically valid (reasoning via contradiction in Logic).
But I don't think or I think, therefore I do not exist is false. People do exist until death once born, whether they think or not. We know that from the fact of the reality in the world.

Therefore I think therefore I am is false. "I am" has nothing to do with "I think".
I am alive therefore I am, or I see me therefore I am are more meaningful statements.

People often resort to name calling if they are unable to find a way to respond to someone's comments.

I have to say, your patience at trying to get your point across is admirable. I don't think I would have so much patience. I would more likely think, "Let them just believe what they want."

What you are saying always seemed so clear to me, even before I researched how other philosophers criticized Descartes's cogito, I had already come up with similar ideas. — Beverley

Great minds think alike. Fully agreed with your fair and accurate analysis and comment on the point. :cool: :up:

You too, seems not knowing the difference between validity and truth. Something is valid doesn't mean it is also true.
— Corvus

What a clown. Goodbye. — Lionino

Suppose this is a typical response when the hidden ignorance was revealed. :nerd:

So in a sense I agree with you that the syllogism "I think, therefore I am" is really not a good example of syllogism — Fire Ologist

We seem in agreement there even if not in complete degree. Well, that's a progress suppose.
Thank you for your input on the point.

But "I think therefore I am" or better put, "thinking 'I am'" to myself demonstrates the objective fact of thinking as content in the world. The world is just very small, objectively comprised of me thinking "I am." — Fire Ologist

This is true. It is real to you, but it is nothing to me. Likewise, you would never know what I am thinking. It is true and real to me, but nothing to you. Therefore it is why, I think therefore I am is a subjective statement. It is a psychological mumbling or monologue, or as Banno put it correctly, an intuition to oneself.

When someone said, I think therefore I am, it doesn't mean a thing to me. I can only presume, that the person is making some mumbling noise to himself.

I exist, because I see me visually, hear me talking to the other people, and they talk back to me in reasonable manner and interacting with the world as per cause and effect principles, not because I think I am.

I know X exists, because I can see it, touch it and feel it. Not because I think it exists.

Thinking is objective content. It’s an instance of general being sought as a ground for something to know. — Fire Ologist

Thinking is a subjective mental activity. Content of thinking is private with no access possibility to other minds. To the owner of the mind, thinking is realistic. But to the rest of the world, thinking mind of you is an unknown entity. Until you demonstrated your thought contents with your actions or linguistic expressions, your thinking has no existence apart from to your own mind.

Even if you have demonstrated your thoughts publicly indirectly using your actions and linguistic expressions, the other minds wouldn't have 100% direct knowledge of your thought contents.

Therefore I think therefore I am is a meaningless statement to the rest of the world, and it is not an objective statement.

I see me therefore I am, would be a more meaningful statement. Because at least someone else could verify your existence visually against your statement.

That means nothing in this context. You can change it to https://www.umsu.de/trees/#(p~5q)~2(p~5~3q) or https://www.umsu.de/trees/#(p~5q)~2(~3p~5q) and it remains valid. — Lionino

Of course it is valid. Hence the assumption, Not P -> Not Q is valid. That was all it was trying to present. You too, seems not knowing the difference between validity and truth. Something is valid doesn't mean it is also true.

Curious, you were just saying how Bogart is not god. In any case, I already proved how this is in full agreement with Descartes: — Lionino

I never said Bogart was no good. I said Bogart was not a god. You seem to keep distorting the facts habitually. His point can be taken where it proves my point in the argument, but Bogart is not a god, and he is not no good. I don't know he is good or not good, and I know he is not a god.

Thinking → existing
I think
Therefore I exist — Lionino

There is no logical ground to deduce Thinking -> Exisiting.
I think therefore I exist is nonsense.

As I said before, Logic can only show you if the arguments and conclusions are derived from the premises. It cannot tell you the propositions themselves are true or false. You must get the truths or falsity from the real objects, situations and events in the world.

Cogito cannot be examined for truths. Therefore it is a meaningless statement, and Cogito ergo sum is a false statement based on the meaningless premise.

You are back to your nonsense sophistry again. Bye~

I am telling you this again mate. Logic will only show you whether the propositions were derived correctly or not from the assumptions, and that's all. Nothing more.

The truths must be checked out with the reality in the world i.e. the events, objects and situations.
I think therefore I am is a psychological statement. How do you check "I" think of someone else apart from your "I"? It is a contradiction.

It is just to show that Not P then Not was validly drawn from P -> Q. That is all.

You don't seem to know what valid means. Valid just means conclusion was derived from the premises. It doesn't mean conclusion is true.
A statement can be valid, but it could still be false. P -> Q is FALSE.

This is why I advised you to read some basic Logic books. It is not about the symbols.
The basic concepts on Logic seem lacking in your writings.

His view of the condition of truth being found outside of what 'belonged' to oneself was brought together with needing to make decisions that shaped what life will be. Our ability is directly involved with those choices. — Paine

He considered as absurd the philosophical and theological attempts to prove/disprove the existence/nonexistence of God. Instead, the commitment to live an authentic Christian life must be rooted in a "leap of faith." And so one who lives an authentic Christian life is the Knight of Faith. — Arne

Great points. Thanks for your replies. :cool: :up:

You wrote
(I think, therefore I exist) or (I don't think, therefore I don't exist)
All your friends need do is deny the right of the disjunct - which they have done. — Banno

Sure, good point.  They disputed that Not P -> Not Q doesn't make sense. But the logic checker says it is valid.

(p→q)∨(¬p→¬q)
(P -> Q) = -P or Q (P. Bogart)

We know and they even admit that Not Q = False
So it must be P -> Q = Not P or Not Q
P-> Q = False (proves I think therefore I am, is false).

Because Cogito is a psychological statement or intuition, it is very awkward to prove its validity using first order logic.

It is like a psychological statement, I feel happy, therefore I dance.
The statement is an obscurity itself.  Who is "I"? And what does "I" feel happy about? We don't know.

The same goes with Cogito ergo sum. I think therefore I am. Who is the "I"? and What is the content and object of "think" in there. It is unclear. The only "I" know, is my "I", but I think I am doesn't warrant I am. Rather, what I see, feel, sense, remember and reason is a warrant for my existence. And it is absolute a private state of mentality.

We would never know anything about the state or nature of Cogito, who it belongs to or what the Cogito was about.

Perhaps for this type of purely psychological statement logical analysis, it would be better to use Kripke frame,  Epistemic or Intentional Logic, and check for its validity.  It would turn out to be invalid for sure.

Just was suggesting a would-be better formula. Not biting your hands at all.
My point was the content of Not Q was FALSE, therefore the original assumption P -> Q is False.
The 3 dualists have been havering with their muddled examples which didn't make any sense at all.
I agree cogito is not a logical statement, and it looks doubtful if it is even an inference.

He's been called the Grandfather of existentialism. He drew attention away from grand project building (like Hegel) to the experience of being alive: to that 'quality of being that comes to rest in the sanctuary of the form.' — frank

He had all the symptoms. His primary concern was on the existence of the individual. Anxiety, dread, authenticity. . . . He was a significant influence on Heidegger. — Arne

K. seem to have had close connection to Christianity and God in many of his writings. How does his concept of God fit into existentialism?

Corvus' argument here is of course invalid - tragic that this should need saying. — Banno

Your formula seems incorrect. This is the correct one.

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.

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?

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.

: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.

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.

The evidence that you are psychologically biased is based on the fact that, you don't even accept my proposition that we can agree to disagree, and end the discussion. Because obviously no matter what logic and explanations were offered to you, you cannot see it, or accept it. The only way for the closure would be we agree to disagree. That is a fair solution. But you refuse to accept it.

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:

Fully agreed — flannel jesus

Good :nerd:

I agree with your idea that language is a tool to communicate, and it can be unclear at times for philosophical discussions.  But we also have  Formal Logic which can aid in clarifying the obscure ideas, statements or propositions.

But at times, Formal Logic can also present ambiguous conclusions due to its limitations. Hence it is good to have both tools, and use them together when one is lacking in the clarification process.
This is especially the case with the classic symbolic logic.  It can sometimes mislead the folks or be abused for presenting illogical sophistry as truth.  That is the reason why there are so many different types of Logics available for us to use e.g. Modal Logic, Fuzzy Logic, Epistemic, Dynamic, Intentional, Institutional, Description Logic .... etc.

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.

For your question do we need a unified language in Philosophy? I would say No. It won't make difference what language or formal logic you use. If some folks are psychologically biased on something or some ideas, then no logic, no reasoning and explanation can change his views or enable them the point. IE psychology overrides reasoning in philosophy in some cases.

I agree. For Sartre, individual existence is freedom. For Heidegger, individual existence is being-in-the-world. For Nietzsche, individual existence is will to power. — Arne

Was Kierkegaard an existentialist? In what sense yes or no?

Destruction is purely physical, whereas violence is physical plus psychological.
Therefore attributing violence to the natural disasters sounds absurd.
Violence can only be attributed to the agents with psychological motives and sufferings.
Violence can happen without physical destruction e.g. in mental level.

I don't see any possible relevance or link between art and violence.
Likewise, I can't see any link between art and destruction. They are not relevant in any shape of forms.

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.