Secrets played a central role in transformations in medical and scientific knowledge in early modern Europe. As a new fascination with novelty began to take hold from the late fifteenth century, Europeans thirsted for previously unknown details about the natural world: new plants, animals, and other objects from nature, new recipes for medical and alchemical procedures, new knowledge about the human body, and new facts about the way nature worked. These 'secrets' became popular items of commerce and trade, as the quest for new and exclusive bits of information met the vibrant early modern...