Sagan, C. (1996). The Demon-Haunted World: Science as a Candle in the Dark (pp. 304-306). New York: Balantine Books.
A radio interview with Carl on these topics is available. His Baloney Detection Kit is also available.
At the heart of science is an essential balance between two seemingly contradictory attitudes--an openness to new ideas, no matter how bizarre or counterintuitive, and the most ruthlessly skeptical scrutiny of all ideas, old and new. This is how deep truths are winnowed from deep nonsense. The collective enterprise of creative thinking and skeptical thinking, working together, keeps the field on track. Those two seemingly contradictory attitudes are, though, in some tension.
Consider this claim: As I walk along, time--as measured by my wristwatch or my aging process--slows down. Also, I shrink in the direction of motion. Also, I get more massive. Who has ever witnessed such a thing? It's easy to dismiss it out of hand. Here's another: Matter and antimatter are all the time, throughout the Universe, being created from nothing. Here's a third: Once in a very great while, your car will spontaneously ooze through the brick wall of your garage and be found the next morning on the street. They're all absurd! But the first is a statement of special relativity, and the other two are consequences of quantum mechanics (vacuum fluctuations and barrier tunneling, they're called). Like it or not, that's the way the world is. If you insist it's ridiculous, you'll be forever closed to some of the major findings on the rules that govern the Universe.
If you're only skeptical, then no new ideas make it through to you. You never can learn anything. You become a crotchety misanthrope convinced that nonsense is ruling the world. (There is, of course, much data to support you.) Since major discoveries at the borderlines of science are rare, experience will tend to confirm your grumpiness. But every now and then a new idea turns out to be on the mark, valid and wonderful. If you're too resolutely and uncompromisingly skeptical, you're going to miss (or resent) the transforming discoveries in science, and either way you will be obstructing understanding and progress. Mere skepticism is not enough.
At the same time, science requires the most vigorous and uncompromising skepticism, because the vast majority of ideas are simply wrong, and the only way to winnow the wheat from the chaff is by critical experiment and analysis. If you're open to the point of gullibility and have not a microgram of skeptical sense in you, then you cannot distinguish the promising ideas from the worthless ones. Uncritically accepting every proffered notion, idea, and hypothesis is tantamount to knowing nothing. Ideas contradict one another; only through skeptical scrutiny can we decide among them. Some ideas really are better than others.
The judicious mix of these two modes of thought is central to the success of science. Good scientists do both. On their own, talking to themselves, they churn up many new ideas, and criticize them systematically. Most of the ideas never make it to the outside world. Only those that pass a rigorous self-filtration make it out to be criticized by the rest of the scientific community.
Because of this dogged mutual criticism and self-criticism, and the proper reliance on experiment as the arbiter between contending hypotheses, many scientists tend to be diffident about describing their own sense of wonder at the dawning of a wild surmise. This is a pity, because these rare exultant moments demystify and humanize the scientific endeavor.
No one can be entirely open or completely skeptical. We all must draw the line somewhere. An ancient Chinese proverb advises, "Better to be too credulous than too skeptical," but this is from an extremely conservative society in which stability was much more prized than freedom and where the rulers had a powerful vested interest in not being challenged. Most scientists, I believe, would say, "Better to be too skeptical than too credulous." But neither is easy. Responsible, thouroughgoing, rigorous skepticism requires a hardnosed habit of thought that takes practice and training to master. Credulity -- I think a better word here is "openness" or "wonder" -- does not come easily either. If we really are to be open to counterintuitive ideas in physics or social organization or anything else, we must grasp those ideas. It means nothing to be open to a proposition we don't understand.
Both skepticism and wonder are skills that need honing and practice. Their harmonious marriage within the mind of every schoolchild ought to be a principal goal of public education. I'd love to see such a domestic felicity portrayed in the media, television especially: a community of people really working the mix -- full of wonder, generously open to every notion, dismissing nothing except for good reason, but at the same time, and as second nature, demanding stringent standards of evidence -- and these standards applied with at least as much rigor to what they hold dear as to what they are tempted to reject with impunity.
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