Listen, shit head poseur , if P is false, and (P-> Q) is all you've got, then you have no grounds for opening your fucking mouth about Q being true even if P is false.

SO SHUT THE FUCK UP.

(August 29, 2012 at 1:50 pm)Chuck Wrote: Listen, shit head poseur , if P is false, and (P-> Q) is all you've got, then you have no grounds for opening your fucking mouth about Q being true even if P is false.

SO SHUT THE FUCK UP.

Are you... Typing to me? Btw, nice Anomalocaris avatar.

(August 29, 2012 at 1:50 pm)Chuck Wrote: Listen, shit head poseur , if P is false, and (P-> Q) is all you've got, then you have no grounds for opening your fucking mouth about Q being true even if P is false.

SO SHUT THE FUCK UP.

We weren't talking about when I'd have grounds for claiming that Q is true. We were talking about whether the conclusion of a logical inference is true if and only if the premises are true.

I never said that if P is false, and all you have is (P -> Q), then I have grounds for "opening your fucking mouth" about Q. You're tilting at strawmen.

(August 29, 2012 at 1:41 pm)CliveStaples Wrote: That is demonstrably false. Consider the following:

i. P (premise)
ii. P -> Q (premise)
iii. Therefore, Q (conclusion)

This is a valid logical argument; if P and (P -> Q) are both true, then Q must also be true. However, it is not necessarily true that the conclusion holds only if the premises do:

i. Barack Obama is in Washington, D.C. (Premise)
ii. If Barack Obama is in Washington, D.C., then Barack Obama is in the United States. (Premise)
iii. Barack Obama is in the United States. (Conclusion)

This, again, is a valid logical argument; if (i) and (ii) hold, (iii) must necessarily follow. However, (iii) could be true even if (i) and (ii) didn't hold; hence "(iii) only if [(i) and (ii)]" is false.

Yes, the conclusion can be true even if the premise is false. I presume in your example that Barack Obama is somewhere n the USA, but not in Washington DC. So your premise can be false and your conclusion true...by coincidence.

(August 29, 2012 at 2:07 pm)Mister Agenda Wrote: Yes, the conclusion can be true even if the premise is false. I presume in your example that Barack Obama is somewhere n the USA, but not in Washington DC. So your premise can be false and your conclusion true...by coincidence.

QED.

(August 27, 2012 at 6:01 am)greneknight Wrote: The usual question that I get asked is why I am a Christian. It's obvious. I was brought up a Christian and I've been an altar boy since I was 5. Naturally I would be a Christian. If I had been born in Saudi, I'd be a Muslim altar boy today.

You'd make a great atheist. And welcome, by the way.

That's the irony, isn't it? The ones who would make good atheists also make pretty good Christians.

Oh, it's something I knew nothing about. My head...

(August 29, 2012 at 1:41 pm)CliveStaples Wrote: I disagree; I think that anyone who makes a claim has the burden of supporting it. If I'm going to say, "There isn't any evidence that the world is round," I need to support my characterization of the available evidence.

I think that is incorrect. That's because there is already a huge body of evidence that the world is round. If you compare that with theism, when someone says there is no evidence for God's existence, the fact is there is really no evidence for God in the first place. So your analogy is unfair.

It's true. The onus is on the chap who says the world is round. And he has evidence for that. Abundant evidence. In our age of space travel, the evidence is incontrovertible.

Quote:That is demonstrably false. Consider the following:

i. P (premise)
ii. P -> Q (premise)

You may not use logic to prove the truth or falsity of a proposition, only the validity of an argument.

Quote:I think that anyone who makes a claim has the burden of supporting it.

I agree

Quote:If I'm going to say, "There isn't any evidence that the world is round," I need to support my characterization of the available evidence.

I agree. That is why I make no claims; I assert only "I do not believe, due to a lack of credible evidence. [OF WHICH I AM AWARE} I attract no burden of proof.

It seems we may need to agree to differ. I have limited interests in your sophistry. My position is: God cannot be argued into or out of existence. Show me your proof or stop wasting my time and fuck off