In the life of the great philosophers and thinkers of all times is often found the key to better understand their ideas. The biographical fact thus becomes part of our lives. Even knowledge, said Nietzsche, has a life and a story. Not an abstract succession of doctrines and writings but a comparison with the real lives of the authors and their fellow human beings, always facing the ever imminent experience of death that besieges every human attempt. Passions, intentions, disputes that go beyond the accidental biographical fact to become part of our own life.