From the 6th century BCE, philosophy was used to make sense of the world – including astronomy, mathematics, politics, ethics, metaphysics and aesthetics. But why did philosophy flourish in Greek culture? How were the great philosophers received in their own time? And how did it influence Islam, communism and even the theories of Sigmund Freud? Rob Weinberg puts the big questions about history’s biggest thinkers to Professor Angie Hobbs at the University of Sheffield.