Gilbert Harman

Like Glenn Shafer, we are nostalgic for the time when “philosophers, mathematicians, and scientists interested in probability, induction, and scientific methodology talked with each other more than they do now”, [p.10]. 1 Shafer goes on to mention other relevant contemporary communities. He himself has been at the interface of many of these communities while at the same time making major contributions to them and this very symposium represents something of that desired discussion. We begin with a couple of general points about issues several commentators have raised and then discuss other more particular issues

Two conceptions of a priori methods and assumptions can be distinguished. First, there are the assumptions and methods accepted prior to a given inquiry. Second, there are innate assumptions and methods. For each of these two types of a priori methods and assumptions, we can also allow cases in which one starts with something that is a priori and is justified in reaching a new belief or procedure without making any appeal to new experiential data. But we should not suppose there is some further sort of a priori explained in terms of some other notion of justification. If we try to construct a notion of the a priori by considering ways in which knowledge, belief, or reasoning might be though to be directly a priori, via direct insight, inability to imagine something false, intentions about use of language, and the language faculty, the resulting conception of the a prior in each of these cases reduces to either of the first two conceptions.

INTRODUCTION In my view, justice is entirely conventional; indeed, all of morality consists in conventions that are the result of continual tacit bargaining and adjustment. This is not to say social arrangements are just whenever they are in accordance with the principles of justice accepted in that society. We can use our own principles of justice in judging the institutions of another society, and we can appeal to some principles we accept in order to criticize other principles we accept. To use David Hume's model of the relevant sort of convention, two people rowing a boat each continually adjusts his or her rate of rowing to the other so that they come to row at the same rate, a rate that is normally somewhere between the rate at which each would prefer to row. In the same way the basic principles of justice accepted by people of different powers and resources are the result of a continually changing compromise affecting such things as the relative importance attached to helping others as compared with the importance attached to not harming others. Hume's rowers provide an example of a “convention” that is normally completely tacit. There are other models in which the bargaining can be more explicit, for example when a seller comes to set prices that are acceptable to customers, when employers reach understandings with employees concerning wages, or when political groups influence legislation. I want eventually to consider the implications for moral reasoning and argument of the thesis that principles of justice are entirely the result of implicit bargaining and convention of this sort.