Basehor, Kans.--Read The Republican Brain on the Republican Brain and laugh, weep, or scream.
For an even more nuanced approach, something that conservatives in general and Republicans in particular don't seem very capable of, watch a video of Jonathan Haidt's work.
As Justice Learned Hand once penned, "The mark of a free man is that ever-gnawing inner uncertainty as to whether or not he is right." And Julian Huxley, "To become truly adult we must learn to bear the burden of incertitude." This idea seems to be almost anathema to conservatives, who see the world in black/white, right/wrong, either/or, yes/no, my-way-or-the-highway terms.