How could a pious, Christian mystic spread radical Enlightenment ideas and freedom of thought? Johann Konrad Dippel was a radical pietist, an alchemist, a philosopher, a medical doctor, a renegade, a firebrand. He was also one of the most-read authors of early eighteenth-century Europe. Born at the Burg Frankenstein in the South of Germany, he was a truly cosmopolitan figure, straying between France, Berlin, the Netherlands, Denmark,...