Talk:Correlation does not imply causation

Jump to navigation Jump to search

This Logic related article has not received a brainstar for quality. Please consider expanding the article appropriately. See RationalWiki:Article rating for more information.

Archives for this talk page: , (new)

Wouldn't Bible prophesy be a VERY good example of this?

The bable stated in the last days people would sin, and since people are currently sinning, bible prophesy is true. Is this a (blatant) example of this?--TemplarJLS (talk) 07:16, 10 September 2014 (UTC)

Murky example is not murky; just bad

Yes, obesity is not the cause of diabetes. But it is a probable risk factor unto itself, as the "Risk factor" section notes. Adipose tissue triggers insulin resistance and inflammation, which are themselves causative factors for diabetes. Drawing a distinction between central obesity and other forms is just a red herring.

The "risk factor" section covers the obesity-diabetes overlap better (and I improved it further). However, the talk about risk factors being symmetric is a classic causation boner: even if A causes B, B does not necessarily cause A.--Fire Me Boy (talk) 05:21, 3 November 2014 (UTC)

Ah, beat me to it! I was trying to find a different murky example to take its place. Noir LeSable (talk) 05:58, 3 November 2014 (UTC)

Nitpicking: (P&Q) ≠ (P→Q) ٧ (Q→P)

Technically the above is correct, but a bit more accurate formula for the implication would be:

(P&Q) → (P→Q) ٧ (Q→P)

And it just happens to be a tautology. Which mostly proves that one can't really discuss causality via propositional logic. I suppose there is a certain aesthetics in decorating article about a logical error with some erroneus logic, but I'm not sure if it was intended? 95.221.194.28 (talk) 18:51, 9 December 2014 (UTC)

Yeah, but see, there's a reason we use ≠, right? Because the notions themselves aren't logically identical. You can't just go through a proof and replace all instances of (P&Q) with (P→Q) ٧ (Q→P), and still prove the same things. It's one of the classes of errors people make in using the idea. Ikanreed (talk) 19:01, 9 December 2014 (UTC)
So, for someone a little less conversant with PQ style statements, is it that the article version is a literal statement of the title while the BoN version shows what one would conclude after making the error? It's not necessary that I understand, but I want to! MarmotHead (talk) 21:49, 9 December 2014 (UTC)
(P→Q) ٧ (Q→P) causes the truth value of Q and P to be the same. (P&Q) causes the truth value of Q and P to be both true. They are therefore not equivalent, but if "(P&Q)" is true, then "(P→Q) ٧ (Q→P)" will also be true. The more limited case is also an example of the general case, but this relationship only goes one way.--TiaC (talk) 22:14, 9 December 2014 (UTC)
Thanks! I was trying to parse it linguistically, but your explanation (from programming?) is much more straightforward. MarmotHead (talk) 22:21, 9 December 2014 (UTC)
No guys, you're wrong. The BoN had it right. (P→Q) ٧ (Q→P) is a tautology, because if P is false, then the former statement is true, if q is false, the latter statement is true, and if both P and Q are true, then both sides of the or statement are true. It doesn't ascribe equality to P and Q, it's just a universally true logical statement. Like (P v ~P). Ikanreed (talk) 17:49, 10 December 2014 (UTC)
Oh fuck, that's an or, not an and. You're quite right.--TiaC (talk) 18:33, 10 December 2014 (UTC)
At any rate, the fact that it's the summary quote is misleading, and the logic isn't sound. I'm gonna take BoN's advice and scrub it. Ikanreed (talk) 20:15, 10 December 2014 (UTC)
Why not just change it to (P&Q) ≠ (P→Q)? People don't use the fallacy to claim bidirectional implications.--TiaC (talk) 20:18, 10 December 2014 (UTC)
Because as the anon explained, the notion of logical "and" isn't the same as the observational idea of co-incidence. Nor is the theoretically application of causation the same as the logical notion of implication. You can't actually express the true notion without first order logic, and even then, it wouldn't be intuitively meaningful. It's probably best to save the formal logic where it is strictly applicable. Ikanreed (talk) 20:23, 10 December 2014 (UTC)
Ok, sounds good.--TiaC (talk) 20:29, 10 December 2014 (UTC)

Another example

This is an example from real life. There was an article in 2013 in Denmark about a guy who'd "discovered a wonder-remedy" against snails in his garden. He'd discovered that the snails wouldn't invade any flowerbeds he'd put dead moss in, so after this discovery, and this is seriously what it says in the article, he used ironsulfate to kill the moss in his lawn, removed the moss and tossed it into his flowerbeds. The expert who was consulted, said that she'd never heard of this before, but couldn't deny there could be something in dead moss that kept snails away. So following this article, the advice of course spread to various gardeners and forums. Use dead moss against snails.

The funny thing is, I found another article posted five years earlier... About how somebody coincidentally discovered that snails are killed by ironsulfate.