" Sehnsucht? The German word is rich with emotional and imaginative associations, famously described by the poet Matthew Arnold as a “wistful, soft, tearful longing.” And what of the “Blue Flower”? Leading German Romantic writers, such as Novalis (1772–1801) and Joseph von Eichendorff (1788–1857), used the image of a “Blue Flower” as a symbol of the wanderings and yearnings of the human soul, especially as this sense of longing is evoked—though not satisfied—by the natural world. "

― Alister E. McGrath , C. S. Lewis: A Life: Eccentric Genius, Reluctant Prophet