Abstract: Precious few texts on art survive from the High Middle Ages; most are excerpts, taken from sources like letters, chronicles, or exegetical tracts. As a result, the practice of art-making in the Middle Ages remains mysterious, its guiding principles often ascribed to religious imperative. One of the only complete treatises on art to survive from the period is On Diverse Arts, or, in Latin, de diversis artibus. Written by a monk under the pseudonym Theophilus in the early twelfth century in northern Germany, the treatise provides three books of instructions on the arts of painting, stained glass, and metalwork, introducing each with a prologue rich in religious interest. Since the treatise was first brought to scholarly attention by Gotthold Lessing in 1774, it has been treasured as a rare resource on the history of artistic technique; it has been seen as a compilation or a collection of recipes, an unlearned text that confirms the myth of the medieval artist as a pious, humble craftsman. A close look at the text and manuscripts, however, reveals a different story: On Diverse Arts, I argue, is in fact a carefully composed, highly learned treatise with a clear narrative and agenda. In this paper I look at Theophilus’ descriptions of technique and explore his concept of artistic skill. When read within the context of twelfth century thought, a distinct theory of artistic practice begins to emerge, and a relationship between virtue and skill becomes evident.