Meehl on theory testing, never gets old.

The position of Popper and the neo-Popperians is that we do not “induce” scientific theories by some kind of straightforward upward seepage from the clearly observed facts, nor do we “confirm” theories as the Vienna positivists supposed. All we can do is to subject theories—including the wildest and “unsupported” armchair conjectures (for a Popperian, completely kosher)’— to grave danger of refutation…

A theory is corroborated to the extent that we have subjected it to such risky tests; the more dangerous tests it has survived, the better corroborated it is. If I tell you that Meehl’s theory of climate predicts that it will rain sometime next April, and this turns out to be the case, you will not be much impressed with my “predictive success.” Nor will you be impressed if I predict more rain in April than in May, even showing three asterisks (for p < .001) in my t-test table! If I predict from my theory that it will rain on 7 of the 30 days of April, and it rains on exactly 7, you might perk up your ears a bit, but still you would be inclined to think of this as a “lucky coincidence.” But suppose that I specify which 7 days in April it will rain and ring the bell; then you will start getting seriously interested in Meehl’s meteorological conjectures. Finally, if I tell you that on April 4th it will rain 1.7 inches (.66 cm), and on April 9th, 2.3 inches (.90 cm) and so forth, and get seven of these correct within reasonable tolerance, you will begin to think that Meehl’s theory must have a lot going for it. You may believe that Meehl’s theory of the weather, like all theories, is, when taken literally, false, since probably all theories are false in the eyes of God, but you will at least say, to use Popper’s language, that it is beginning to look as if Meehl’s theory has considerable verisimilitude, that is, “truth-like-ness.”

Meehl, P. E. (1978). Theoretical risks and tabular asterisks: The slow progress of soft psychology. Journal of Consulting and Clinical Psychology, 46, 806–834. doi:10.1037//0022-006X.46.4.806