Inevitably, much has been left out of my history. I have chosen to focus on those great voices which have, in my judgement, either said something radically new or expressed old ideas with fresh vigour. Several towering figures are conspicuous by their absence, most notably Dante, Petrarch, Shakespeare and Kierkegaard, because at least some of the ideas that inform their works appear elsewhere in my account, and because I lack the space and competence to cover them all.