Donald Trump's most fervent supporters consisted of elements of the Republican coalition as it has developed over the last several years. These elements are characterized by the form of their beliefs. They confidently hold beliefs without regard to the full set of relevant arguments and evidence.
Some of their beliefs are admittedly based on "faith", which means that they are held confidently despite the absence of reasons that would matter to others who do not share their faith. These include both moral and factual beliefs: homosexuality is sinful; humans did not evolve from other animals; abortion is equivalent to murder.
Other beliefs are accepted uncritically, without considering arguments on the other side, or, worse, attributing those arguments to a conspiracy. The belief that global warming is not caused by human activity is a prime example. Conspiracy theories about collusion by scientists guarantee that all arguments on the other side can be ignored. Thus, the holders of these beliefs have no way to discover that they might be incorrect, since all counter-arguments seem to come from a diabolical conspiracy. People hold these questionable beliefs with high confidence and are thus willing to impose them on others, through their political action.
These beliefs have been supported by talk radio and Fox news. In turn, these sources are supported and encouraged by more traditional Republicans. We saw this influence earlier in the "Tea Party" movement, which feeds back into the content of these sources.
More generally, these beliefs are the result of a pattern of thinking. People who hold them are lacking in what I have called actively open-minded thinking (AOT). AOT involves self-critical reflection. In order to be confident of a belief, we must look actively for reasons why it should be rejected, modified, or held with less confidence. If beliefs go unchallenged by this sort of reflection, we have no reason to know that they deserve high confidence. We have no way to distinguish those that would survive critical reflection from those that would not.
Note that AOT is not equivalent to reflection in general. Some reflection is nothing more than bolstering, looking for reasons why we were right all along, finding ways to make everything fit with our preferred conclusion. AOT concerns the direction of reflection, not just its amount. The ultimate aim is to be fair to counter-arguments.
Nor does AOT require that we never hold beliefs with high confidence. Often, an active search can find little to say for the other side, or can lead to a modified form of the original belief that is designed to deal with problems.
AOT is built in to the scientific method. Science as an institution works to look for holes in current theories. Scientists get credit for finding such holes, and ways to plug them by modifying or discarding the theory in question. For these reasons, we should have more confidence in the conclusions of science than we have in the conclusions of ways of thinking that do not involve such self-criticism. More generally, our confidence in experts should depend on how much their expertise comes from AOT.
AOT is apparently affected by cultural support. Higher education tends to support it (imperfectly, to be sure). I have been using a short questionnaire (based on a longer version devised by Keith Stanovich and his collaborators) that measures people's support for AOT. It has questions such as: "Allowing oneself to be convinced by an opposing argument is a sign of good character"; "Changing your mind is a sign of weakness" (reversed); "People should search actively for reasons why their beliefs might be wrong"; and "It is important to persevere in your beliefs even when evidence is brought to bear against them" (reversed).
I and my collaborators have found that people who score low on this scale (opposing AOT) tend to score high on Jared Piazza's measure of belief in "divine command theory", the idea that God's laws are beyond the capacity of humans to fully understand and thus must be obeyed without question. Such a view is consistent with the sort of faith that leads people to advance moral views through politics even when they cannot argue for those views in terms that make sense to those who do not share their particular faith.
Dan Kahan has collected data with our AOT questionnaire for a representative sample of the U.S. adult population. People low in AOT tend to rate themselves as more politically conservative and more strongly Republican. (The result is described at the end of this paper) This result is unusual because the same data set finds no correlation at all between conservatism and another measure of cognitive style, the Cognitive Reflection Test (CRT), a set of tricky arithmetic problems that is supposed to measure the tendency to reflect on initial conclusions. But I think the CRT is heavily influenced by mathematical knowledge, and it also tends to assess willingness to spend time on a problem rather than a self-questioning attitude as such. It does not specifically assess the willingness to look for reasons why a pet belief might be wrong. In sum, the results for the AOT show that, in current U.S. politics, conservatives really do think differently, in ways that help us understand their attachments to weakly supported conclusions about facts and morality.
"Conservatives" in the U.S. tend not to think that AOT is a good thing. Many think it is OK to defend their beliefs as if they were possessions. Kahan did not look at Trump supporters in particular. (The data were collected a few years ago.) But it seems likely that this negative attitude toward AOT is more common in this group than in Republicans in general. Many people who identify themselves as conservative Republicans are very clear about their acceptance of AOT, although they tend to emphasize different issues when they discuss details. And, likewise, some liberals or progressives have the same negative attitude, although not as many of them, at the moment.
On the optimistic side, my student Emlen Metz has found remarkably high levels of respect and capacity for AOT in 8th grade students across the U.S. from a variety of schools. It seems that the ideology of AOT has become widespread in the culture of schools. This is good news for the future. We need to take a page from our youth, to look to their desire to learn from each other and their hope in the future. We need to try to get everyone, journalists, teachers, and ourselves, to understand AOT more deeply.
Even those who already favor AOT can benefit from understanding how it helps with communication, by giving us a better understanding of our discussion partners.