Kyburgian Acceptance: A Rejection, Hedged

There seems to be something about probability that offends some people’s (not necessarily Kyburg’s) sense of taste. Not being of this aesthetic persuasion, I can only speculate that assigning degrees of belief to propositions is seen as a cop-out; a true believer should either adopt a proposition or not, eschewing compromise. Those who would reject probability need not deny uncertainty, however. Instead, they argue, one can accommodate the inevitable incompleteness in immediate knowledge by an appropriate belief revision policy. Philosophers have assigned the term acceplance to this notion of categorically adopting an uncertain belief and acting as though it were the case. That acceptance is semantically elusive and technically complicated is evidenced by the volume of philosophical debate on the subject as well as the mass of A1 research on nonmonotonic logic aimed at working it out computationally. That this A1 work is essentially attacking the problem of acceptance is not often explicitly recognized, and Kyburg’s clear exposition of this point is one of his essay’s important contributions. The other, of course, is his own proposed account of acceptance. In taking issue with Kyburg, I attempt first to explain why we might want a theory of acceptance. My claim is that our quest can and should be justified on pragmatic computational grounds, rather than on those purely philosophical (I’m not sure exactly what this means, but I don’t identify it with “frivolous”) or aesthetic. Next, I argue that we cannot have acceptance, at least not in the terms Kyburg seems to want it. Finally, I suggest some ideas that would have to be addressed in order to obtain an account of acceptance worth accepting. Unfortunately, Kyburg ’s proposed acceptance approach comes bundled with all sorts of other baggage, including his own scheme for probability based on interval measures derived from statistical reference classes, as well as the general idea of evidential pr-obability. These are ideas that Kyburg has certainly given a fair run for their money, and it is only natural that his acceptance theory would incorporate them. But since the issues they address are somewhat orthogonal to acceptance per se, I am afraid they confound the main points. In my response I will attempt to focus on the essential stance on acceptance and defer taking issue with other elements of the Kyburg program to some other forum.