I vote against closing, even though the question could have been phrased somewhat more precisely. The importance of our understanding how to perform causal inference cannot be underestimated. Any improvement in our current understanding of this matter could be used to combat many kinds of ills in the world, such as diseases and crime. A very important general question is how to begin with a large amount of observational data about, say, how disease X is caused -- say 10,000 people's health status and auxiliary variables -- and extract the most likely guesses as to the etiology of X.