For example, it turns out (from a very large study) that applying sunscreen has no effect on skin cancer. A likely explanation is that we adjust for constant exposure—staying in the sun about as long as we can without burning.

Mind you, it’s a good heuristic. In fact, most causal discovery algorithms assume it. But it doesn’t always work.

Within this thread the question of causation vs correlation has wavered from a narrow context to the much broader metaphysical debate. Hence there has been a certain amount of confusion. I was taught in statistics that you cannot simply proclaim causation. You need to provide a mechanism or you do end up with a rooster/sunrise fallacy. My position on the larger question is sketched out above.

Thirty-five posts into the thread, and some of us still fail to grasp Hume’s very simple point.

OF COURSE you can infer causation from correlation on Bayesian network models of causation, because they simply define causation in terms of statistical correlation. Refuting Hume with interventionism is like refuting Berkeley by kicking rocks.

Kenny, yes, given a known set of variables, then you could argue just as you have. But it is almost impossible to definitively say that you’ve ruled out all other forms of interference. Which is why the logical arrow, the correlation =>causation contrapositive is much more better, to quote a snippet of Cap’n Jack, and we speak of the essential trait of any good theory, that of falsifiability.

Of course, you can’t eliminate the possibility that you’ve ignored some extra variables that play very important roles in your model, or the possibility that you’ve just got very non-representative data. But that’s just what makes science hard. Controlled experiments are nice for giving you variables where you specifically know there are no incoming arrows, but even in observational (is that the same as epidemiological?) studies, you can sometimes get enough correlations to be sure that some of them are causal.

Of course, I’d still prefer a model of causation that involves mechanisms, but I think you can predict the existence of mechanisms even when you don’t know anything about them. (For instance, see the amazing successes of Darwin and Mendel prior to Watson, Crick, and Franklin.)

Out of curiousity, is there a claim out there that is not often used selectively by people who want to ignore evidence that they find ideologically uncongenial?

I can think of many claims that are used selectively, eg the laws of thermodynamics and creationists, but I can’t think of any claim that is not used selectively.

As for what’s really happening? Isn’t that not science, more in the purview of epistemology? Maybe it’s all red, blue, green, and yellow demons pushing things around asif_ they were being affected by gravity, electromagnetism, etc. So what?

It was the sun, just like with the rooster’s crow. Without the sun nothing would’ve happened. For sure.

All these things we consider when trying to find causation. In the end WE determine which is the most logical ‘cause’ of the event. Some people may say the drivers negligence while driving, while others may say his addiction to smoking. It is all about perspective.

I do agree that causation is just correlation because it is such an ambiguous idea that it cannot be pinpointed to an exact incidence. Very good post.

A good article on this topic is by Ardon Lyon called ‘Causality,’ The British Journal for the Philosophy of Science, Vol. 18, No. 1 (May, 1967), pp. 1-20.