One problem I note is that "I" is not well defined. Does "I" refer to some immaterial thing which interacts with the pineal gland?

Of course we all have some conception(s) associated with "I", but how accurate is that conception? — wonderer1

I don't think it matters how we conceive "i". We could say "if something thinks it must exist", and as I already said, "if something does anything at all it must exist". The idea of existence seems to be implicit and ineliminable in thinking of any activity at all.

But this is not the argument Corvus presented in the quote. — Banno

What do you think his argument is? Couched in plain English would be good.

no, he would get caught up on the word "then" as a time signifier. — flannel jesus

Okay, I hadn't thought of that.

...where does that premise come from? — flannel jesus

The premise is invalid. But it is not a contradiction. That is, it seems possible. (But it has been a long few days and I may be wrong).

@Corvus' logic has been less than impeccable - we all make errors. But again, while he has not shown that the Cogito is invalid, no one else has managed to show that it is valid.

What do you think his argument is? — Janus

I'm not going over that again. Time to move on. Corvus is wrong, but perhaps not in the way folk have suggested; and that he is wrong does not imply that therefore the Cogito is valid.

The premise is invalid. But it is not a contradiction. That is, it seems possible. — Banno

Of course it's possible, it's equivalent to saying a <-> b, and there's many a and b for which that's true.

But the cogito doesn't say a <-> b, it just says a -> b.

So how is Corvus turning a -> b into (a -> b) -> (not a implies not b)? We already know, because he told us. He says any logic textbook will show, modus ponens means you can deny the Antecedent.

that he is wrong does not imply that therefore the Cogito is valid. — Banno

I don't think anybody has that train of thought

it's equivalent to saying a <-> b — flannel jesus

No, it isn't.

I can prove it

Go on, then. Here is the premise:

P - > Q — Corvus

or in my parsing

(t→e)→(¬t→¬e) — Banno

Show how that is equivalent to A↔B.

https://www.umsu.de/trees/#((t~5e)~5(~3t~5~3e))~5((t~5e)~5(t~4e))

I slightly misstated the argument. If (t→e)→(¬t→¬e) holds, as a general rule, then all (t→e) are actually (t↔e).

any time you have (t→e) and (¬t→¬e), you have (t↔e).
https://www.umsu.de/trees/#((t~5e)~1(~3t~5~3e))~5(t~4e)

I slightly misstated the argument. — flannel jesus

Fine.

If (t→e)→(¬t→¬e) holds, as a general rule, then all (t→e) are actually (t↔e). — flannel jesus

But...

Yes, I slightly misstated the argument, as I said.

(t→e)→(¬t→¬e) isn't itself equivalent to (t↔e), it's equivalent to saying "if you have an implicaation (t→e), it's safe to say (t↔e)". He's turning ALL implications into bidirectional implications. Which has some absurd consequences.

https://www.umsu.de/trees/#((t~5e)~5(~3t~5~3e))~5((t~4e)~5(t~5e))

That doesn't mean much, you can just have the right side on it's own and it's already valid.

https://www.umsu.de/trees/#(t~4e)~5(t~5e)

I'm not sure what you're getting at with that.

It shows (I hope...) that your

(t→e)→(¬t→¬e) isn't itself equivalent to (t↔e), it's equivalent to saying "if you have an implicaation (t→e), it's safe to say (t↔e) — flannel jesus

is valid. If trivial.

I don't think it's trivial. It means denying the Antecedent, if applied as a universal rule, has genuinely absurd consequences.

That doesn't mean much — flannel jesus

I don't think it's trivial — flannel jesus

Make up your mind! :wink:

I'm out, I think. Too tired to think.

(Which can be seen in what I just wrote...)

those two quotes are about different things. Goodnight

Go on, then. Here is the premise:

P - > Q
— Corvus
or in my parsing

(t→e)→(¬t→¬e)
— Banno

Show how that is equivalent to A↔B. — Banno

Why do you want to prove (t→e)→(¬t→¬e) is equivalent to A <-> B?

You too are missing the point here.
As you put, your conclusion Cogito is invalid is correct, but your logic seems to be missing the critical point in your reasoning.

You got explain in detail what you are exactly trying to do when you are asking (t→e)→(¬t→¬e) is equivalent to A <-> B, and I will tell you where you got it wrong.

he was replying to me, not to you. He was asking me to prove something. He quoted you so I appreciate why you would think he was asking you.

He quoted my ID in his post, so the Forum emailed me saying that Banno quoted me in his post, so I was replying to him. Well, he thinks my reasoning is wrong, so I was going to point out where he got wrong after hearing what he has to say about it.

I'm just saying, the bit about a <-> b is directed at me, not at you.

But do you not see him saying my logic is wrong? I am trying to find out where he got the idea. It is good that he agrees 50% with me, but his logic has problems that he doesn't seem to see.

I'm gonna go out on a limb here and say he probably doesn't agree with your reasoning there because (p implies q) implies (not p implies not q) is not generally true - it's called Denying the Antecedent, and you can't just do that to any ol argument. There are some arguments you can do it for, but it's not generally applicable to all (p implies q) premises.

He's asleep I believe, so he can answer you himself later

My discussion to Banno is totally separate matter to yours, as I am only interested in clarifying Banno point in his logic at this particular stage.

Let's see what he has to say about it.

he probably doesn't agree with your reasoning there because (p implies q) implies (not p implies not q) is not generally true - it's called Denying the Antecedent, and you can't just do that to any ol argument. — flannel jesus

But do you not understand the fact P -> Q has not TF value at the stage? You shouldn't be brining in some internet truth table here. This is tragic that it has to be explained again and again because you seem to be talking with a thick blanket on your face.

You just said some random goofiness followed by an insult. Where's the logic ?

It was a metaphor. :) But it is far higher class than some of your nonsense insults even with vulgarity in the past.

Right, so once again, unwilling to actually use logic to defend a point, read my posts over and over again until you agree with me, yada yada. Tale as old as time. Can't wait until you're actually ready to start looking at logic.

Where's the logic ? — flannel jesus

Well you insisted, Banno's post was addressed to you, so I will wait until Banno gets up from his sleep, and comes back with his explanations. Then after that I will tell him where he got wrong.