Suppose we grant the assumption that intuitions or ?seemings? count as evidence. Suppose we grant the further, perhaps dubious, assumption that they can tip the balance in their favor in these cases. This implies that there can be disagreements in isolation, each party to a disagreement can be reasonable. However, things are different when we turn to cases of full disclosure. To see why, compare a more straightforward case of regular sight, rather than insight or intuition. Suppose that you and I are standing by the window looking out on the quad. We think we have comparable vision and we know each other to be honest. I seem to see what looks to me like a person in a blue coat in the middle of the quad. (Assume that this is not something odd.) I believe that a person with a blue coat is standing on the quad. Meanwhile, you seem to see nothing of the kind there. You think that no one is standing in the middle of the quad. We disagree. In isolation -- before we talk to each other -- each of us believes reasonably. But suppose we talk about what we see and we reach full disclosure. At that point, we each know that something weird is going on, but we have no idea which of us has the problem. Either I am ?seeing things? or you are missing something. I would not be reasonable in thinking that the problem is in your head, nor would you be reasonable in thinking that the problem is in mine.
Consider Pro and Con once again. Each may have his or her own special insight or sense of obviousness. But once there has been full disclosure, each knows about the other?s insight. These insights may have evidential force. But then there is no basis for either Pro or Con retaining his or her own belief simply because the one insight happens to occur inside of him or her. A point about evidence that plays a role here is this: evidence of evidence is evidence. More carefully, evidence that there is evidence for P is evidence for P. Knowing that the other has an insight provides each of them with evidence.
425 In each case, one has one?s own evidence supporting a proposition, knows that
another person has comparable evidence supporting a competing proposition, and has no reason to think that one?s own reason is the non-defective one. To think otherwise requires thinking something like this: ?You have an insight according to which ~P is true. I have one according to which P is true. It?s reasonable for me to believe P in light of all this because my insight supports P.? This is tenacious and stubborn, but not reasonable.
Thus, the private evidence -- the insights or intuitions -- does not support the view that there can be mutually recognized reasonable disagreements, or even that there can be reasonable disagreements after full disclosure. If the insights count as evidence, once one reaches a position of full disclosure, one knows that there are insights on both sides. It is difficult to see why this evidence better supports one?s own view rather than the competing view, and just as difficult to see how it supports an attribution of reasonableness to the other person. The competing insights cancel each other out.
Those who would appeal to private evidence do have a straw to grasp at. They can insist that one?s evidence that another person has a competing insight is always weaker than one?s evidence that one has an insight oneself. And this, it can be argued, justifies retaining one?s belief. If correct, this would show that there can be reasonable disagreements after full disclosure. It makes it less clear that there can be mutually recognized reasonable disagreements. The reason for this is that if one person, say Pro, is not justified in believing that Con really does have an insight, then Pro is also not justified in believing that Con?s belief is justified. One might resort to the view that Pro is justified in believing that Con does have an insight, but not as well justified in this belief as in his belief that he himself has his own insight. Perhaps a defense of reasonable disagreements along these lines can be worked out. However, I think that the prospects are