by Joan Birman
The following eight letters were written by Dennis Johnson to me during the period of time when he was working on his foundational papers about mapping class groups of surfaces (see [e1], [e4], [e3], [e2], [e5], [e7], [e6], [e8] and [e9]). The letters evoke Dennis as I remember him — filled with life, enthusiasm, curiosity, and eagerness to talk about math. All but one of the eight are undated, but the order in which they were written isn’t very important. He was carving out new areas for investigation, so new that it wasn’t even clear at the time which of the open questions he was considering could or would be answered. They give insight into the creative process, in a way that is easily lost in the essential passage from the letters to the published papers.
The undated letters listed here (below the “References” section) have been provisionally ordered based on internal evidence and on Birman’s memory of her correspondence with Johnson.’s evaluative help in this effort is greatly appreciated.