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Referencing this question and its smart answer:

I'm still confused and the confusion has been in part fueled by "recent" Pearl/Hernán tweets (tweet, tweet and tweet).

Pearl's Ladder of causation and my rephrasing of the third W'question.

  1. Association - What is?
  2. Intervention - What if?
  3. Counterfactuals - What would be if?

Wouldn't interventions that are (perfect) randomized experiments, where two or more groups are treated, each group emulating counter-to-fact causes, not be squarely placed on rung 3.) - all along the Neyman-Rubin potential outcomes framework!? Isn't the potential outcomes framework and a framework for counterfactual outcomes conceptually identical? Pearl says:

Interventions change but do not contradict the observed world, because the world before and after the intervention entails time-distinct variables.

I can understand that interventions of the sort "If we take aspirin, will our headaches be cured" are rung 2.); but then they are not experiments, are they? (Perfect) randomized experiments are set up to compare a factual cause to a contrafactual one. What would be if I'd taken aspirin in comparison to not have taken any - or counterfactual: I've taken aspirin and others have been randomized to not to, so what is the difference in headache averages?

A part of the rung 2.) / rung 3.) "problem" can perhaps be traced back to different taxonomy. The "Harvard group" defines causal inference as:

Causal inference has a central role in public health; the determination that an association is causal indicates the possibility for intervention. (Glass, Goodman, Hernán, & Samet, 2013)

So in their eyes (Hernán's trichotomy: description, prediction (probably rung 1. on Pearl's ladder) and counterfactual prediction=(randomized, perfect) intervention=causal inference (Hernán, Hsu, & Healy, 2019)) they would most probably see interventions on rung 3.) (as "counterfactual interventions" perhaps?).

Which brings me to an interesting very recent intervention by Imbens (Imbens, 2019):

I would have liked to have seen a fourth rung of the ladder, dealing with “why,” or reverse causality questions.

Wouldn't that then call for a reformulation of the Ladder of causation?

  1. Association - What is?
  2. Intervention - What if?
  3. Counterfactual prediction/intervention (experimental or observational, if we could perfectly de-confound) - What would be if?
  4. Counterfactual explanation - Why?; by this I mean all that the other nice things we can do with counterfactuals (Chapter 8 -> The Book of Why; attribution, mediation, generalizability, etc., etc.)

Cheers

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    $\begingroup$ Voting to close as opinion based This is the age-old epistemology and heuristics debate, claiming you have to know why something works to know how it works. $\endgroup$
    – AdamO
    Commented Sep 17, 2019 at 14:14
  • $\begingroup$ Isn't that an opinion in itself, one associating "age old debate" <-> "nothing really new", so rung 1.) on the Ladder of causation? Just wondering.... In effect: there are quite a few taxonomies around these days, not least fueled by the undeniable prominence of The Book of Why. So a reasonable discussion. $\endgroup$
    – nafets
    Commented Sep 17, 2019 at 14:26
  • $\begingroup$ Not quite sure what the opinion filter here is all about. Would suggest reading Causation&Explanation (Stathis Psillos). Theories are sets/web of beliefs and each belief has content that is made up of concepts. Causation in this context is a theory, alot of factual concepts, but a set of beliefs nonetheless. So if its only facts your asking for, there will be no discussion. There is a quite a blunt question asking for expertise at the end of my query: "Is Imbens right or Pearl". See also Intervention by @CarlosCinelli in the referenced post. $\endgroup$
    – nafets
    Commented Sep 19, 2019 at 11:18
  • $\begingroup$ If you reformulate your question to make it more technical, it might be possible to reopen. Regarding the ladder of causation, the criteria in the Book of Why is defined mathematically. More precisely, the rungs are defined based on the type of information on the causal model that you need to answer a query of that level. So, in that vein, what type of extra information do you need to answer your rung 4 query that is not in rung 3? $\endgroup$
    – Carlos Cinelli
    Commented Sep 24, 2019 at 22:40
  • $\begingroup$ You would need to define the type of query (mathematically) and the type of information needed to answer that query (mathematically), then we can see if we can have 4 rungs instead of 3. Hernan is collapsing rung's 2 and 3 into one, for instance, which is ok, but you lose some interesting distinctions. Imbens "reverse causality" seems to fit squarely on rung 3, as questions of actual causation. $\endgroup$
    – Carlos Cinelli
    Commented Sep 24, 2019 at 22:45

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