Suppose that Tom and Sally have a disagreement over a factual question (as opposed to one of values or preferences). She claims that the argument he is making has errors or is unconvincing, but Tom feels the same way about her argument. They debate the question for an hour, but afterwords are still each adamantly convinced that his or her own reasoning is sound while the other person's is flawed. In this instance, is each person really more justified believing in his or her own belief than he or...