Often a person uses some folk proverb to explain a behavioral event even though, on an earlier occasion, this same person used a directly contradictory folk proverb to explain the same type of event. For example, most of us have heard or said, “look before you leap.” Now there’s a useful, straightforward bit of behavioral advice—except that I vaguely remember admonishing on occasion, “he who hesitates is lost.” And “absence makes the heart grow fonder” is a pretty clear prediction of an emotional reaction to environmental events. But then what about “out of sight, out of mind”? And if “haste makes waste,” why do we sometimes hear that “time waits for no man”? How could the saying “two heads are better than one” not be true? Except that “too many cooks spoil the broth.” If I think “it’s better to be safe than sorry,” why do I also believe “nothing ventured, nothing gained”? And if “opposites attract,” why do “birds of a feather flock together”? I have counseled many students to “never to put off until tomorrow what you can do today.” But I hope my last advisee has never heard me say this, because I just told him, “cross that bridge when you come to it.”

The enormous appeal of clichés like these is that, taken together as implicit “explanations” of behavior, they cannot be refuted. No matter what happens, one of these explanations will be cited to cover it. No wonder we all think we are such excellent judges of human behavior and personality. We have an explanation for anything and everything that happens. Folk wisdom is cowardly in the sense that it takes no risk that it might be refuted.

Keith E. Stanovich, How to Think Straight About Psychology, 10th ed. (2013), 14.

ETA: Should have included the subsequent paragraph:

That folk wisdom is “after the fact” wisdom, and that it actually is useless in a truly predictive sense, is why sociologist Duncan Watts titled one of his books: Everything Is Obvious—Once You Know the Answer (2011). Watts discusses a classic paper by Lazarsfeld (1949) in which, over 60 years ago, he was dealing with the common criticism that “social science doesn’t tell us anything that we don’t already know.” Lazarsfeld listed a series of findings from a massive survey of 600,000 soldiers who had served during World War II; for example, that men from rural backgrounds were in better spirits during their time of service than soldiers from city backgrounds. People tend to find all of the survey results to be pretty obvious. In this example, for instance, people tend to think it obvious that rural men would have been used to harsher physical conditions and thus would have adapted better to the conditions of military life. It is likewise with all of the other findings—people find them pretty obvious. Lazarsfeld then reveals his punchline: All of the findings were the opposite of what was originally stated. For example, it was actually the case that men from city backgrounds were in better spirits during their time of service than soldiers from rural backgrounds. The last part of the learning exercise is for people to realize how easily they would have explained just the opposite finding. In the case of the actual outcome, people tend to explain it (when told of it first) by saying that they expected it because city men are used to working in crowded conditions and under hierarchical authority. They never realize how easily they would have concocted an explanation for exactly the opposite finding.