Cicero sets out the three major Greek philosophies: Epicureanism, Stoicism and Aristotelianism (or Peripateticism), by recounting his conversations with Lucius Torquatus, Marcus Cato and Piso.
He then provides his commentary and criticisms of each.
The volume was written in the summer of the year 45 BC a few years before Cicero's assassination at the hands of Mark Antony's men.