forum 2: week of 16 Jan - Lewis
The Rule of Belief captures propositions that the speaker never thought of and yet are possibilities(which include actualities according to Lewis). It can be argued that evidence and arguments would back up any possibility P of that nature, whether or not speaker S believes it, but only if we can provide evidence and arguments for every fact of the world, ie. some principle of sufficient reason. So any P which can be supported by evidence and arguments may not be properly ignored. But this would be of help only if not believing P includes ignoring P altogether.
I think the Rule of Attention might be interpreted to be claiming more than it actually is. Lewis is not claiming that if a possibility is not a feature of the conversation context, then it is properly ignored. He is saying only that a possibility may not be properly ignored if it is a feature of the conversational context. And so a possibility P, if supported by arguments and evidence, may not be properly ignored, even if no attention is paid to it.
But you say there may be a fact that, in principle, S could not draw his attention to, meaning it cannot be the case that S had not drawn his attention to P(else that wold be circular). This would happen when certain evidence and arguments are unavailable for S. Maybe it's true in some sense that certain things are beyond S's understanding, therefore he can't grasp them and they would not count as proper justification. I don't buy it though,.
I am troubled by Lewis' web of rules as well. I think the troubles comes from his method in trying to achieve his goals of reconciliation. His methods in many ways want to mirror empirical ways people come to acquire knowledge. He largely shuns armchair philosophizing in favor or armchair psychology. This is troubling in two ways. First, he is assuming that people fundamentally have a good way of acquiring beliefs and knowledge, and that he is simple trying to come up with a coherent way of explaining an existing phenomena in much the way same science explains nature. So he is not proposing some grand theory which if adopted by everyone, would magically the quality of knowledge in human society. Second, he is trying to cover too many moving and contradictory parts at the same time, and these forces are pulling his argument apart. This makes his argument arbitrary. He has all these rules which, while superficially rendering these disparate views compatible, do not do much to explains their overall coherence. The lack of overarching thematic narratives makes the whole project lack rhyme and reason. The faux-empiricism and arbitrariness makes Lewis's paper a confounded enigma.