Carl Zimmer over at The Loom has a good post today explaining a favorite technique of groups who need to cast doubt on expert knowledge in order to advance their particular agenda. For example, creationists want to convince the public that most biologists, geologists, and, indeed scientists in general, don't really understand their fields; holocaust deniers claim that professional historians have all been taken in by a Jewish fraud; and greenhouse skeptics say the vast majority of climate scientists are just guessing. I've ground my teeth at this technique for years but never had a good name for it. Now I do.
Zimmer describes it this way:
When I ask scientists what's the biggest misunderstanding people have about their work, they often talk about how they know what they know. People tend to think that a scientist's job is to gather every single datum about something in nature--a mountain, a species of jellyfish, a neutron star--and then, simply by looking at all that information, see the absolute truth about it in an instant....
Many bogus attacks on scientific research play on this common misunderstanding of science-as-revelation. If scientists don't know everything they can't conclude anything. Paleoanthropologists have found less than two dozen species of hominids from the past six million years--therefore they can't draw any conclusions about how humans appeared on Earth. Climatologists don't have a perfect temperature record for the planet--therefore they can't say anything about how man-made pollution is warming the atmosphere. In cases like climate change, these bogus attacks spread from science to policy based on science. To hear some people talk, we should only do something about climate change once we have tracked every molecule in the atmosphere since the dawn of civilization and can predict its course for the next thousand years.
The imperfect knowledge gambit is a particularly nasty and effective rhetorical device because it builds on very common misconceptions about how knowledge is created and because it sets the groundwork for a number of follow-up arguments.
Most scientists and historians do not claim to know everything (the ones that do are, by definition, bad scientists and historians (or coaches hired to teach science and history)). If we knew everything, there would be no need for new scientists and historians and they would all have to get jobs making furniture or mowing lawns. Since there is very little demand for bad furniture and uneven lawns, they would become unemployed and sit around all day whining about how hungry they are. This would be even more annoying than their present whining about how unappreciated and underpaid they are, so be thankful that there are still things to find out.
It should be obvious to most people that we do not know everything. But, by harping on the fact that scientists and historians do not possess pure and complete Truth, that their knowledge is partial and provisional, the opponents create an opening for their anti-knowledge. One follow-up argument is to portray their anti-knowledge as equal to our knowledge and demand equal time. This fairness argument is a favorite of creationists and holocaust deniers. Another follow-up argument is the dark horse gambit beloved of conspiracy theorists. This emphasizes the partial nature of knowledge and insists that their anti-knowledge might be the missing explanation that leads to the Truth (at this point they usually compare themselves to Galileo).
The difference between many conspiracy theorists and leading creationists, holocaust deniers, and greenhouse skeptics is that the conspiracy theorists are usually sincere in their confusion, while the latter three are cynically exploiting a rhetorical device to win supporters and advance their agendas. Most conspiracy theorists just want the Truth. Creationists want to introduce religion into the schools and don't care what damage they do to the educational mission. Holocaust denial is usually just an introduction to the larger anti-Semitic program. The do-nothing conclusion of greenhouse skeptics is to the direct benefit of corporate and political agendas. All things being equal, I'd rather spend time with a Velikovsky follower or amateur Templar historian than any of those three
Note I was probably overly subtle in distinguishing between leaders and supporters in that last paragraph. Aside from their rhetorical methods, I lump creationists, holocaust deniers, and greenhouse skeptics together because I view all three groups as being led by cynical manipulators. The individual followers are often sincere and convinced by the rhetorical tricks of their leaders. Many are open to intelligent counter-arguments and eager to understand. The leaders of these three movements, on the other hand, are patently dishonest and have only my contempt.