The Book of Why: The New Science of Cause and Effect (Penguin Science)

by Judea Pearl

I like the image that Fisher Box provides in the above passage: Nature is like a genie that answers exactly the question we pose, not necessarily the one we intend to ask. But we have to believe, as Fisher Box clearly does, that the answer to the question we wish to ask does exist in nature. Our experiments are a sloppy means of uncovering the answer, but they do not by any means define the answer. If we follow her analogy exactly, then do(X = x) must come first, because it is a property of nature that represents the answer we seek: What is the effect of using the first fertilizer on the whole field? Randomization comes second, because it is only a man-made means to elicit the answer to that question. One might compare it to the gauge on a thermometer, which is a means to elicit the temperature but is not the temperature itself.