Last week, a friend pointed out an inadequacy in my terminology. I referred to people who do not believe in evolution. She pointed out that we should refer to people who do not know about evolution. The creationists and the advocates of intelligent design are just plain ignorant.
If we take a couple of reasonably uncontroversial principles, that knowledge implies true belief and that doxastic voluntarism is suspect, we can unpack this a little.
Given that the broad evolutionary account is true, and that there is a stack of evidence for it, and that research institutions and practices are such that we probably would not believe it if it were false (satisfying a tracking condition), those who do believe it and who are sufficiently in touch with the progress of science that they would become aware of major changes in the direction of thought, also know it. And those who do not believe it certainly do not know it, because knowledge requires belief.
Then we come on to the accusation of ignorance. This is not, in this context, a mere accusation of failure to be aware. The creationists and the advocates of intelligent design do know about evolution, to a limited extent. They are aware of the evolutionary account in outline, and of some of the evidence. But they claim to have weighed the evidence and to have rejected evolution.
It is easy to suspect them of straightforward doxastic voluntarism. It looks very much as though they have decided to reject evolution, and have then deliberately misread some evidence, and ignored other evidence, in order to support that position. The obvious motive would be to bolster their position within a group of people, usually a religious or religious-political group, who take pride in something that from the outside can be seen to be intellectual perversity. The perversity is a great instrument for distinguishing between the in-group and the out-group. If you can only join by professing to believe something that goes against the grain of rational thought, that gives the group a certain exclusivity.
There is, however, another twist. It seems unlikely that many people could live with naked doxastic voluntarism. That is why flat-Earth societies and the like have very few members. It would be almost as hard to live with a nakedly selective choice of evidence, to know that one had looked at certain fossils but had deliberately ignored others.
I suspect that what allows those who reject evolution to live with themselves is the fact that the evidence is far more subtle and extensive than a collection of fossils in a glass case. We have genetic mechanisms, features of the genome that can be traced across species, the geographical distribution of species, and so on. One needs some understanding of genetics, of molecular biology, and of mathematics, to grasp the significance of all that evidence. So those who lack such understanding can overlook the evidence without deliberately rejecting it.
That is where we should level the charge of ignorance at creationists and at the advocates of intelligent design. They simply do not know enough to grasp the evidence. My friend was correct to say that they do not know about evolution, but primarily because knowing about it means more than knowing the rough outline. That is also why it is so hard to convert them to good sense. They need to go back to school first.
Sometimes, one observes the same phenomenon in other fields. I once knew someone who was utterly convinced that something supernatural was going on when people walked across glowing coals. It had to be, because the coals were at a thousand or so degrees. I tried to explain that while the temperature was high, the thermal energy that was held by the coals was low, so the temperature of the coal-walker's feet did not rise to a thousand degrees. (Do not try this at home: it can go wrong, and people do get badly burnt.) Alas, she just did not have the concept of thermal capacity, and probably did not have the concept of energy as it is defined within physics.