The Sidney Greats lecture series is designed to provide introductions to great books and ideas to members - undergraduates, graduates, Fellows and staff - of Sidney Sussex College, Cambridge, giving them an opportunity to learn and think about ideas in fields other than their own. The introductions are provided by academics, and the speakers are chosen not necessarily because of their particular specialism in the field but because of their ability to communicate the importance of the subject to a general audience. In making these lectures available to the public as podcasts, we very much hope to encourage a wider audience to embark on their own explorations of these subjects.