I was able to create a chart of my theoretical schemes, and I noticed that there were holes in the chart. And I predicted the existence of the particles to fill the chart. And those all worked. But then the question was: Was there some sub-unit out of which all of these particles were made? These strongly interacting particles. Well I tried it, and it came out that you could do it with a certain set of particles, and in a quite economical way. But they would have to have electrical charges, +2/3 and -1/3. And of course, all known particles had integral charges, in units of the proton or electron charge. The proton is called +1, the electron is called -1. And all the known particles had charges of +1 or -1, or possibly +2 or -2, and so on. Nothing had a fractional charge. But these sub-units — that would give the most economical scheme for making what we saw out of hidden sub-units — these sub-units would have charges of +2/3 or -1/3. I was initially discouraged, but then I made a visit to Columbia University, and a colleague there, Bob Serber, asked me whether I had ever considered this economical way of making sub-units, considering what you then called a triplet. And I said, “Yes, I have considered it, but they come out to have fractional charges.” And I showed him the fractional charges on a napkin in the faculty club in Columbia, where we were having lunch. And then, thinking about it during the rest of the day, it occurred to me that if they were completely hidden, these particles, if they never came out, but they were permanently trapped inside the known particles, then it wouldn’t cause any difficultly, any disagreement with observation or with any fundamental theoretical idea. And so I began to put it forward.