Seneca's Letters to Lucilius are a rich source of information about ancient Stoicism, an influential work for early modern philosophers, and a fascinating philosophical document in their own right. This selection of the letters aims to include those which are of greatest philosophical interest, especially those which highlight the debates between Stoics and Platonists or Aristotelians in the first century AD, and the issue, still important today, of how technicalphilosophical enquiry is related to the various purposes for which philosophy is practised. In addition to examining the philosophica