Dear All,
There is a very interesting paper in the January issue of the International Journal of Epidemiology, which discusses the pitfalls of the Counterfactual Theory (http://www.ncbi.nlm.nih.gov/pubmed/26800751). The authors argue that some study designs which do not strictly adhere to the Counterfactual Theory also have merit and place in causal inference (think Less Commonly Used Observational Study Designs which we discussed in Week #4).
An article which further discusses this topic also appeared in today's issue of EpiMonitor (http://epimonitor.net/Counterfactual-Movement.htm).
Lydia