Benedict de Spinoza lived a life of blameless simplicity as a lens-grinder in Holland. And yet in his lifetime, he was expelled from the Jewish community in Amsterdam as a heretic, and after his death his words were first banned by the Christian authorities as atheistic, then hailed by humanists as the gospel of Pantheism. His "Ethics Demonstrated in Geometrical Order" shows us the reality behind this enigmatic figure. First published by his friends after his premature death at the age of 44, the "Ethics" uses the methods of Euclid to describe a single entity, properly called both "God" and "Nature", of which mind and matter are two manifestations. From this follow, in ways that are strikingly modern, the identity of mind and body, the necessary causation of events and actions, and the illusory nature of free will.