"Of course, I just...well...never mind. I have been corresponding with those Bernoulli brothers rather a lot. Nothing important. You know I have always been fascinated with symbols and characters. The calculus has brought us new ideas for which we want new symbols. For differentiation, I like a small letter d , and for integration, a sort of elongated S . That’s how the Bernoullis have been doing it, and it suits them well. But there is another Swiss mathematician, a fellow who was once viewed as quite a promising young savant-in-the-making, by the name of Nicolas Fatio de Duillier."