Indeed I'm not claiming that only randomized trials can be believed. But where they are possible and have been done, they should play a large role in the discussion of causality. It no longer makes sense to discuss PK and RM without reference to a large body of evidence that has come along since. I find the vast majority of the arguments against the use of RCTs to be attacking strawman positions that randomistas don't make, or to be equally applicable to all forms of evidence. But that's a side point. The real question here is on what we should be focusing on in this particular debate. To paraphrase from your comments, Martin, I would put it this way: I only wish the authors (Pitt and Khandker) had been more humble about their findings of causality and made their data and programming public when they announced their findings. It would not seem to have been too hard for them to have seen the errors in their causal claims and prevented misunderstandings and misinterpretations. That is a lesson for us all, including randomistas and observationists.