'To review books, as those of us who press this task upon our colleagues well know, is to enact academic generosity, part of the voluntary reciprocity that still sustains universities in these increasingly hard and pressured times. Even if a write-up is unsympathetic, contents still have to be read, and there is little official reward for the gifting of time, wit and wording energy required for crafting a response. To have my recent book on Darwin taken up by the five people of the calibre enlisted here is thus more than humbling: something rare, motivating and invaluable has been honoured in the assembling. That they express things in a way I wish I had — oh, for the chance to plagiarise and rewrite the original! ' (Introduction)