Diatribe de progidiosis crucibus is a 1661 work by the Jesuit scholar Athanasius Kircher. It was printed in Rome by Blasius Deversin and dedicated to Archduke Leopold Wilhelm of Austria. A second edition of the work was published in Rome in 1666 and a German translation appeared in Gaspar Schott's Joco-seriorum naturae et artis (Würzburg, 1666). Diatribe is Kircher's most succinct and explicit statement in favour of seeking rational causes for phenomena through an understanding of natural laws, derived from observation, rather than seeking miraculous explanations. This continued the theme he had taken up in Scrutinium Physico-Medicum (1658) and pursued in greater detail in Mundus Subterraneus (1665). Background On 3 July 1660 an eruption of Vesuvius began. A plume of ejected material rose up to 4 km into the air and was carried off to the southeast by the wind. As was normal for Vesuvius, the late stages of the eruption involved the ejection of white ash. Along with this ash, free twinned augite phenocrysts were ejected, causing small cross-shaped objects to fall from the sky. This phenomenon appeared on the day the Sun entered Leo (21 July). The population of Naples believed at first that these crosses were a sign from their patron saint, Saint Gennaro, that he would protect them from the volcano. However many people in southern Italy soon grew fearful that the crosses were a token of God's anger. Kircher wanted to undertake an investigation of the phenomenon that would reassure people and help avoid panic. He had an intense dislike of superstition and its simplistic view of the world, which led people to prefer the idea of the disruptive intervention of a miracle rather than seeking to understand the complex mechanisms by which the world and nature operated. He had a prior research interest in Vesusius, having had himself lowered into its crater for research purposes in 1638. Between August and October of 1660, Kircher travelled to the hamlets of Somma and Ottaviano to look for primary evidence himself, and also read accounts from other witnesses in southern Italy. These reported various extraordinary discoveries, such as that the crosses had appeared on altar drapes, and on objects inside locked chests and shuttered rooms. Discussion and conclusions The first two thirds of the work consists of a pars historica and a pars physica, setting out both a historic narrative of the phenomenon and a physical description.