This cours addresses key presocratics from Heraclitus to the sophists, who stand at the origin of philosophy as cornerstone of European spirituality.Readers might find that already at this point we encounter timeless and actual questions concerning the human condition in the world, limits of our knowledge, or the problem of adequate articulation of reality.Later thinkers did not philosophised from scratch, but criticised or were inspired by their predecessors.The cours thus provides an introduction to presocratic thought as an important field of our spiritual history.