In Chicago – I naturally made certain assumptions. One was that there was a difference between baryons and... well, no, let me start differently. One was that there were various interactions: there was gravitation; there was electromagnetism; there was a weak interaction giving rise to β decay, μ decay, μ absorption and strange analogues of β decay and μ absorption. And then there was the strong interaction. And certain particles participated in the strong interaction – like π and nucleons – and others did not – like μ and electrons and neutrinos. Then isotopic spin was presumably applicable to the strongly interacting particles, and the μ had isotopic spin I and the nucleon had isotopic spin one half, and isotopic spin was approximately conserve, but its conservation was broken by electromagnetism because the electromagnetic current had a portion of it which was isotopic spin I and a portion that was isotopic spin zero. So in the emission of a photon you could either conserve isotopic spin or change it by a unit. In the emission of – emission and absorption of – a virtual photon you could violate isotopic spin conservation. That isotopic spin was a good concept for both pions and nucleons was being shown in our own laboratory in the experiments of Fermi and his collaborators. So it naturally occurred to me that isotopic spin might have something to do with the strange particles. The strange particles might be strongly interacting particles participating in the strong interaction, produced copiously because they were strongly interacting – but inhibited from decay, from rapid…  but prevented from decaying rapidly by a conservation law, which was however slightly broken so that they could actually finally decay, but slowly. And I thought maybe isotopic spin was this conservation law that would prevent them from decaying rapidly. Then a strange particle might for example have isotopic spin five halves, if it had only enough energy to decay into a nucleon and one pion – but not two – then isotopic spin would prevent its decay into nucleon plus one pion. But – and here's the catch – electromagnetism would violate the conservation of isotopic spin and then permit it after all to decay – a little bit more slowly into nucleon plus pion, but only a little bit more slowly because electromagnetism is not that weak. So when I proposed this idea and we discussed it in our theory group at Caltech, it became clear that... well, I just discussed it with Goldberger and Adams, not with anyone else; not with Enrico, just with Goldberger and Adams. It was clear that the idea by itself wouldn't work.