This chapter discusses studies on Newton's alchemy. By the time of his death in 1727, Newton had already become an icon of reason in an age of light, recognized for discovering the laws governing gravitational attraction, unveiling the secrets of the visible spectrum, and laying the foundations for the branch of mathematics known today as calculus. However, during the very years when Newton was discovering the hidden structure of the spectrum, he was also conducting private chymical research to find the “inimaginably small portion” of active material that governed growth and change in the natural world, or as Newton says, nature's “secret fire,” and the “material soule of all matter.” The chapter also sets out the book's purpose and provides an overview of the subsequent chapters.