Thus far unpublished even in its original German, Lux intelligibilis. Investigation on the Metaphysics of Light of the Greeks, submitted by Werner Beierwaltes as a doctoral dissertation in 1957, is presented here for the first time in English translation. The English translation of Lux intelligibilis. Investigation on the Metaphysics of Light of the Greeks is accompanied by an introduction to the person and work of Werner Beierwaltes by Claudia D’Amico, as well as by a substantial Essay as PostScriptum by Enrico Peroli, which allow the reader to grasp the enormous contribution of the original text.