Enlightenment and Cloudiness is a history of knowledge about clouds and atmospheric phenomena in the 18th century. What epistemic status does the cloud hold as an object of knowledge? What is the poetic function of the cloudy in epistemological, rhetorical, poetic, and meteorological discourses? Starting from Christian Wolff's German Metaphysics through Descartes' The Meteors to Goethe's meteorological studies and Friedrich von Hardenberg's General Brouillon, Claus-Michael Schlesinger explores how rationality, clarity, light, and thus the Enlightenment as a whole relate to the blurred and unclear knowledge that cloudiness indicates. In the 18th century, various meteorologies engage with the weather as a natural phenomenon. In addition to astro-meteorological approaches, theological-teleological explanations, and weather mechanics are developing.