No group of believers has more reason to be sure of its own good sense than today’s professional scientists. There is, or should be, no mystery about why it is always more rational to believe in science than in anything else, because this is true merely by definition. What makes a method of enquiry count as scientific is not that it employs microscopes, rats, computers or people in stained white coats, but that it seeks to test itself at every turn. If a method is as rigorous and cautious as it can be, it counts as good science; if it isn’t, it doesn’t. Yet this fact sets a puzzle. If science is careful scepticism writ large, shouldn’t a scientific cast of mind require one to be sceptical of science itself?There is no full-blown logical paradox here. If a claim is ambitious, people should indeed tread warily around it, even if it comes from scientists; it does not follow that they should be sceptical of the scientific method itself. But there is an awkward public-relations challenge for any champion of hard-nosed science. When scientists confront the deniers of evolution, or the devotees of homeopathic medicine, or people who believe that childhood vaccinations cause autism—all of whom are as demonstrably mistaken as anyone can be—they understandably fight shy of revealing just how riddled with error and misleading information the everyday business of science actually is. When you paint yourself as a defender of the truth, it helps to keep quiet about how often you are wrong.…At the end of her book “Science: A Four Thousand Year History” (2009), Patricia Fara of Cambridge University wrote that “there can be no cast-iron guarantee that the cutting-edge science of today will not represent the discredited alchemy of tomorrow”. This is surely an understatement. If the past is any guide—and what else could be?—plenty of today’s science will be discredited in future. There is no reason to think that today’s practitioners are uniquely immune to the misconceptions, hasty generalisations, fads and hubris that marked most of their predecessors.…Happily, there is another way out of the impasse between fallible science and even-more-fallible non-science. The contest is not a zero-sum game: the shortcomings of science do not make it rational to believe cranks instead. It’s a fair bet that many of today’s scientific beliefs are wrong, but only your grandchildren will know which ones, and in the meantime, science is the only game in town.
Well, yeah. Seems like an unnecessarily roundabout way of arriving at that conclusion, but okay. I’m not sure how many people there are who hold some belief in the infallibility of today’s science; I certainly don’t know any myself, and I suspect a lot of them have straw sticking out from their raggedy shirtsleeves and pantlegs in any event. Too often, though, when you hear someone placing emphasis on the imperfect nature of science, it’s being used as a way of trying to keep a foot in the door so that their preferred illogical, irrational belief can sneak back in.
You’re at some large gathering. Noisy, crowded, lots of things to pull at your attention. You hear what sounds like a familiar voice in the general din, turn and see someone through the haze and crowd, standing with her back to you, and recognize her as your friend. You decide to mischievously surprise her with a sly pinch on her ass. One close look and one stinging slap to the cheek later, you realize your mistake. If you’re René Descartes, the lesson you take away from this, and one that is for some reason treated with the utmost respect and gravity by important thinkers for centuries to come, is that your senses can be misleading and therefore can’t be trusted to give you absolute certainty. But how do we know that the senses can mislead us? By further application of the very same senses. You realized that wasn’t your friend after getting close enough to see her shocked face and hear her voice more clearly as she yelped in outrage, using the same eyes and ears that initially gave you the wrong impression. There’s no other method for obtaining that information.
In the same way, we discover our mistakes in science by continuing to apply the same standards of evidence and rationality. There is no divine revelation, no thunderclap of sudden awareness from out of nowhere that clues us in. It’s true that there is no absolute certainty (or at least no way for us to know of it, if you want to throw a bone to Kant here), but science has the reputation it does because it’s repeatedly proven itself to be the best way we know to get reliable, practical understanding of the reality we inhabit. Whatever shortcomings or failures it has to own up to do not mean the door is open to any incoherent fantasy or wishful thinking being just as epistemologically valid.