There was a fourth project which Murph and I regarded, or at least I regarded as very important, but it never got anywhere. I thought of it as my principle occupation during this time and I deviated from it occasionally to work on strangeness, dispersion theory and the renormalization group. The main thing I was doing was this project with Murph, on trying to do a… a field theory without perturbation theory with other approximations, maybe strong coupling or something of that kind. What we did was to omit closed loop, or at least–well, no, not necessarily closed loops. We omitted meson-meson interactions in meson theory. So we were dealing with pseudo-scalar meson theory, which people thought was right with the pion being the meson and having isotopic spin 1, and being pseudo-scalar and so on and so on and so on. But we wanted to look at relativistic pseudo-scalar meson theory, and do something with it that was not just perturbation theory. But in order to make some kind of an approximation that would make the problem manageable we dropped meson-meson scattering. All the remaining diagrams we wanted to sum with a simple formalism. And we did it by constructing a field theory of… in which the square root, essentially the square root of the Feynman propagator for the… for the meson was put in multiplying a creation operator, and then its complex conjugate was put in multiplying a destruction operator. In this way we were able to reproduce all of the diagrams other than, that didn't include meson-meson scattering, from a closed form.

[Q] Was this related to the Thulo type of model?

No, because it was fully relativistic.

[Q] When, let's see, when did they do that? I have..?

 I'm not sure, ’53, ’54, ’53, no, ’54…

[Q] But there was a lot of interest at that period..?

...’54, I think. I think it was ’54, ’55.

[Q] ‘54 was it? But during that, those, the early ‘50s everybody was doing these?

Well we were all in it. Everybody thought that pseudo-scalar meson theory was a good theory and that we should try to calculate…

[Q] And finding new ways, non-perturbative ways of..?

Non-perturbative ways of calculating–that was the sort of standard problem to work on. Except for Enrico [Fermi]. Enrico said, ‘What makes you think this is the right theory?’ And we couldn't understand his attitude. He had some, he and Frank Yang published some weird–what we considered a very weird idea–that the mesons might be bound states of nucleons and anti-nucleons, which was in a way a forerunner of the idea… Exactly, I was going to say… …that they were bound states of quarks and anti-quarks. But most of us regarded that as very weird and what we wanted was to be able to solve pseudo-scalar meson theory in some approximation that was non-perturbative and serious. So Murph and I constructed this formalism which would add up all the diagrams without closed loops, and we could even put in some closed loops by including a fancier propagator for the meson. And then we tried to find a strong coupling approximation, as well as the weak coupling. The weak coupling of course was just perturbation theory without closed loops. The strong coupling we didn't know what, whether it was going to be. Well, we worked off and on on that, but it didn't really get anywhere and of course the…  since the theory was totally wrong, it didn't really matter whether, what we accomplished on it. In the meantime these three diversions were all quite important.