Emanuel Swedenborg's system of correspondences is one of the most influential theories in the history of ideas. Instrumental in the rise of Romanticism, Symbolism and Modernism, and cited as key to the work of Goethe, R.W. Emerson, Honor de Balzac, Charles Baudelaire, Wassily Kandinsky and Arnold Schoenberg, to name but a few, it offers to poets, artists, writers and composers a blueprint for navigating the gap between the material world and non-material values. In this brief introduction, Gary Lachman gives an accessible overview of the many fascinating ways in which Swedenborg's idea has impacted upon the past 250 years.