RICHARD and I are sometimes presented as being highly critical of each other. Those who hope for bloody gladiatorial contests are disappointed when they discover that the circles of our interests and beliefs overlap much more extensively than they had believed. Obviously we disagree about some matters, as I shall describe later. Nevertheless, the disagreements are generally teasing and affectionate, since we are old friends, and have not taken on the character of those bitter wrangles that can disfigure the face of academic life.
For my part, I have much to be grateful to Richard for what he has done. Like numerous other academics working in university biology departments I have taught a great many students who were inspired to take our courses at Cambridge because they had read The Selfish Gene. Matters that had puzzled Darwin, such as self-sacrifice, were made clear to them and they discovered about conflicts between the sexes and generations where previously they had not appreciated that any existed. The language of genes' intentions employed by Richard helped them to deal with the complicated dynamics of evolution. 'Untestable!', grumbled some hard-nosed colleagues from disciplines concerned with physiological mechanism. But they didn't understand. Such explanations are not meant to be treated in the way usually employed by an experimental scientist; they provide a framework in which