[pjmorris]

Have a look at the literature on how smoking was established as a cause for cancer. You can't ethically intervene to have non-smokers smoke long enough to develop lung cancer. A lot of money and intellectual effort was spent on correlation not equaling causation in this case.

I'm no expert on the literature here, but Peter Norvig mentions the smoking-cancer example in his article on experiment design [0]. He gets to the same place the causality people do; observational studies.

[0] https://norvig.com/experiment-design.html