A few weeks ago there was a minor flamewar on Twitter about the alleged abuse of the term causality in various social-science fields, and after the destruction of a small galaxy or two, it ran out of fuel. But this semester I directed an undergraduate honors thesis that used a difference-in-difference approach to a policy question, and I want to put a stake in the ground about the term causality. This is to avoid the future destruction of small galaxies and promote more peaceful gatherings of social scientists.
Here’s the gist: econometric techniques that clearly identify causal relationships target a very specific type of causality, what we might term sufficient-conditions effects in the sense that they identify sufficient causes (if you do X, you will see Y). This sufficient-conditions effects is different from necessary-and-sufficient causes (only doing X will result in Y, and nothing else will budge Y without doing X). But because sufficient-conditions effects is an awful phrase, I propose the following:
Yoda causality: do, or do not. There is no why.
And now the gory details: