The following is an extract from the transcript of the panel discussion at the end of the Proceedings of the 1996 Boston University Conference on the Conceptual Foundations of Quantum Field Theory (ed. Cao, CUP). Read it ... and lament that you don't work in a subject that is characterised by such a strong sense of ethical solidarity. (N.B. Well that's how it looked until I read Lee Smolin's The Trouble with Physics ... sigh.) Audience: What bothered me as a physicist is the question why in the standard model are there so many phenomenological parameters? I mean all these coupling constants, all these masses. I think it should also bother you. So the question is why we are so optimistic that we are on a good track anyway. Weinberg: Welcome to the club. Shelly and I and others and Sidney have been saying for years that the standard model is clearly not the final answer. It has 18 free parameters- Glashow: I have 19. Weinberg: He has 19, all right. I think the point is a similar point. And we know that that means it's not a final theory. But it's pretty good. I mean, it accounts for an awful lot of nature. It's true it's more parameters than appeared in Newton's theory of gravitation. But look how much more of nature it accounts for. We know what it is, it's a stopping point; it's a waystation on the way to a better theory. We know that. Fisher: But do you believe that there is any chance that, for example in string theory, you will be able to calculate at least some of these parameters that they will appear somehow? Weinberg: Yes, David. Gross: Yeah, there's a hope. I mean, Shelly said, and I said the same thing about the standard model. It's more than just that there are 19 parameters, it's the feeling that the theory, as it is now, and with any minor modification of it, and probably any improved field theory, is not going to explain those parameters, or is going to have more parameters. There are beautiful attempts, for example, Georgi and Glashow's attempt at SU(5) unified theory, which answered some of the questions- Glashow: And introduced many more parameters. Gross: -by doubling, no, tripling the number of parameters. So the general feeling, my feeling, and Shelly, although he's not a proponent of string theory, agrees that just going on with quantum field theory a la standard model, is not going to deal with the parameter question. Coleman: Well, the Technicolor people feel it will. Gross: No, of course not. They're in an even worse situation. Are you kidding? They have to introduce- Glashow: They add more and more architecture and none of the architecture is constrained- Coleman: You're right. I was thinking of their first hopes. Gross: But if you go to unified theories that produce Technicolor theories, you have to have more and more parameters. Glashow: But David, it's very important to remind the audience, because they don't know it as well as we do, that despite the fact that there are 19 parameters, most of which play very little role in anything often observed. More like four or five parameters have to do with all of physics, including nuclear physics. We get a perfect explanation of the physical world up to our ability to calculate it, with this theory. The damn theory works. And that is the greatest frustration to non-string-theory people, because how can we be asked to do things any better when we're doing things as well as we could possibly do? The string theory people want to come in and say, well, your methodology cannot possibly do any better, try ours. Our response to that is, well, maybe yours is the right way, but maybe there's a third way. Gross: Well, they're not in contradiction. Glashow: No. Gross: The only point I wanted to make again about string theory is that one of the claims of string theory is that, as far as we know, it is a theory in which all dynamical parameters, all parameters in the theory, all dimensionless parameters in the theory, are dynamical. All coupling constants appear in string theory as the vacuum expectation value of certain dynamical objects. Thus, as far as we know, all parameters in this theory, unlike field theories, are determined by the dynamics. Therefore, the theory has the potentiality of calculating all those parameters. So you ask, why haven't we calculated anything? Roughly speaking, the situation is that our knowledge of string theory is very primitive and will probably change, and we don't yet probably have a handle on the theory as a whole. At the moment, it appears that these dynamical parameters are sitting in a potential well which is flat. And the dynamics just says that they can sit anywhere in that potential well. And every place they sit is equally possible with our control of the dynamics, and at every place they sit, there's a different value for their expectation value of those dynamical objects, therefore a different coupling constant or a different mass for the electron and so on. We don't yet have control over the dynamics which we would hope, as in all other quantum mechanical systems, lifts this degeneracy and picks a unique state and would fix all those parameters. Now that might never transpire, and there might still be ambiguity left even after we know what picks the correct vacuum, the correct solution of this theory. But at least string theory has the possibility of doing that. And that's a new feature of string theory, one which is not so often discussed as the fact that it includes quantum gravity, but for me this is one of its most attractive features- Glashow: David, can I ask you a question? Gross: -it offers the possibility that quantum field theory doesn't, of setting-- Glashow: No. You have a dream. You and your colleagues who do strings have a dream that you will have a unique theory, that the 19 parameters will be one or zero. But have you ever had the following dream, that 75 years pass, and you're quite an old man, and finally the string theory has been worked out, and you've figured out how it all goes, and you've got all these numbers, and the fine structure constant comes out to be 17? [laughter] Gross: It's called a nightmare. Weinberg: I'd like to comment on the exchange between Shelly and David in two respects. One is kind of a sedative remark, and that is that there are obvious tactical differences among the people at the table. I think this remark is really directed to the philosophers and the historians here, rather than to the physicists, who I think already know what I would say. There are tactical differences here. Shelly is skeptical about the future of string theory. David is very enthusiastic. I tend to agree more with David on this, because I've taken the trouble to teach courses in string theory, although I haven't contributed anything to it. But you know, I don't think there's any ideological differences, as compared to tactical differences. That is, if a string theory tomorrow, based on fundamental principles, without ad hoc assumptions, turned out to predict a low energy theory which was the standard model, and gave the right values for the parameters, everyone at the table would regard that as a tremendous triumph. And then if Shelly's nightmare took place, David would probably give up. We know, my point is, and again, I don't think this is something that's any surprise to the physicists, but may be some surprise to philosophers of science who think, in terms of externals and social settings and so on, putting us in a historical context, we are ideologically different. We really score theories the same way. You know we really are the same kind of physicist. Deser: Some better than others. But all of them are opportunistic, when it comes to theories. Weinberg: Opportunistic, yes, we're all opportunistic, that's right. Fisher: I want to say, 'Hear, hear' to that, because I think it is a very important point that all serious theoretical physicists share the same values. Deser: Resolved. Weinberg: But believe me, a lot of philosophers don't agree with that, don't understand it, and think we are some kind of tribal island society, where we're working out a kind of social evolution toward a hierarchical pecking order. Deser: And Steve has thought very much about this problem, has written some very good things on it in case you want to follow up. I think it's a very important remark to the nonphysics side of the audience.