I’m not sure what you mean by “the validity of the suspected cause-effect”; I assume you are referring to the validity of a causal claim? Although I’ve touched on validity (without naming it) here by discussing issues of confounding, it is not important to this explanation. This is necessarily a simplification of a very narrow and specific issue. I may discuss validity at a future date, although I certainly would not attempt to apply it to causal inference in a blog post. There are some very thick books written on the subject that take time and study to understand.

I’m not sure of the relevance of “causal conditions”; these are descriptors of different causal items but not, as you point out, defining. Whether these conditions occur sheds no additional light on the validity of the suspected cause-effect.

In my experience the most ignored element when association is elevated to causality is the importance of any occurrence of non-association. In medical papers it is standard procedure to go from association to the ambiguous “risk factor” to causation without ever discussing evidence that failed to show association. Showing non-association is vastly more powerful than showing association. All 300 years of demonstrations of Newton’s laws of Gravity became suspect with just one orbit (Merccury) that did not show sufficient association between theory and data.

Thank you for this. I teach an undergraduate methods course and I would like to use this post in my class. Please do not take it down anytime soon!

Mike