In a number of conversations between myself and Howard Margolis it has always been clear to me that he did not understand my point of view. He apparently thinks that I do not understand his, and I must concede that this is possible. This puts me in some difficulty in the joint role of author and editor because if I understand him properly, once again, I am not sure that I do, he is making an elementary mistake and therefore I should not have published his paper. If, on the other hand, I do not understand him properly, then this reply is misguided and should not have been published. In view of the importance of the subject, however, and the fact that we do seem to continually misunderstand each other, I thought that bringing the debate out in the open would be worthwhile. Perhaps some of the readers of this journal can either decide who is misunderstanding whom or perhaps explain both of us to the other. To begin with the elementary mistake, the demand curve that economists draw is literally the demand curve, i.e. what the person demands with no attention whatsoever to why he demands it. Thus, if some individual has two different motives for demanding something or other, we simply look at the sum of these two motives when we draw the demand curve. We may, of course, and indeed it is not particularly uncommon among economists, decide that we would like to disentangle the two component parts of his demand and in doing so we might draw in two partial demand curves. In Margolis's case, there are two component demand curves, one by the individual for himself, and as a second his interest in having other people get the right amount of the public good. The demand curve referred to in 'The Demand Revealing Process', however, is simply the total demand that the person has for the public good. It is indeed true that most economists having observed the functioning of the market and government for some time tend to think that most people, most of the time, have a demand curve, the overwhelmingly largest component of which is their own selfish desires. None of us, as far as I know, think that is the only component but we do think it is a large enough component, let