At the beginning of the twentieth century, William Butler Yeats was among those writers whose work was influenced by Swedenborg, and one can notice this ‘influence’ in his poetry and in essays alike. In 1914 Yeats composed Swedenborg, Mediums and the Desolate Places (published a few years later, in 1920), where he defined Swedenborg as a "forerunner" of the Romantic movement, despite a style and spirit far removed from being Romantic. For Yeats, Swedenborg gave expression to the deepest manifestations of his soul, his mental state, and his spirituality by means of powerful images, that can be considered very close to those of a Romantic. The evocative power of Swedenborg’s representations of heaven and hell lies in the fact that he drew on an infinite variety of images of the natural world, meticulously collected during his life as a natural philosopher and mineralogist. These images gave a visible and tangible form to manifestations of an inner unconscious for the soul or, in other words, to an invisible "world of spirits," to which, according to Swedenborg, the souls of all human beings belong. For these reasons his imagination was similar to that of poets and artists; he believed that he could establish a bridge between the outside (sight, sensitive perception) and the inside (the movements of the soul, spiritual activity, moral values) and provide the latter, in its complexity and with its many nuances, a concrete existence.