Gilbert Harman

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.

According to moral relativism, there is not a single true morality. There are a variety of possible moralities or moral frames of reference, and whether something is morally right or wrong, good or bad, just or unjust, etc. is a relative matter—relative to one or another morality or moral frame of reference. Something can be morally right relative to one moral frame of reference and morally wrong relative to another. It is useful to compare moral relativism to other relativisms. One possible comparison is with motion relativism. There is no such thing as absolute motion or absolute rest. Whether something is moving or at rest is relative to a spatio-temporal frame of reference. Something may be at rest in one frame of reference and moving in another. There is no such thing as absolute motion and absolute rest, but we can make do with relative motion and rest. Similarly, moral relativism is the view that, although there is no such thing as absolute right and wrong, we can make do with relative right and wrong

I begin by summarizing the first two chapters of (Harman 1986). The first chapter stresses the importance of not confusing inference with implication and of not confusing reasoning with the sort of argument studied in deductive logic. Inference and reasoning are psychological events or processes that can be done more or less well. The sort of implication and argument studied in deductive logic have to do with relations among propositions and with structures of propositions distinguished into premises, intermediate steps, and conclusion. Deductive logic is not a particular psychological subject and is not a particularly normative subject, although one might attempt to develop a logic of belief or a deontic logic, for example.