This idea that the whole world is just made out of electrons, or particles like electrons, is so attractive, and yet, why should there be two electric charges? But then we discovered that if you have a particle going one way in time, and that turns around and comes backward in time, it behaves as if it had the opposite electric charge and was going in the normal way in time. So that was the idea of electrons and positrons. You might say if you have an electron here and a positron here, and they come together and annihilate, that's it. But an alternative way to look at it; to say it's an electron here, that goes up and turns around and goes back here. It doesn't make this annihilation business be so spectacularly different from ordinary deflections for particles. That idea sounds novel; actually, the Swiss physicist, Stückelberg, had published an idea along that line, I found later, already. And in later life I was able to go and call on Stückelberg -- he's no longer living -- and that was quite remarkable, because he's the only person I'd ever met who was a Knight of Malta. Somehow that relic of the Holy Roman Empire still persisted and he had received this order. A very unusual man, he lived in Geneva.