The mental leap from Galton to Pearson is breathtaking and indeed worthy of a buccaneer. Galton had proved only that one phenomenon—regression to the mean—did not require a causal explanation. Now Pearson was completely removing causation from science. What made him take this leap? Historian Ted Porter, in his biography Karl Pearson, describes how Pearson’s skepticism about causation predated his reading of Galton’s book. Pearson had been wrestling with the philosophical foundation of physics and wrote (for example), “Force as a cause of motion is exactly on the same footing as a tree-god as a
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