Iulius Firmicus Maternus (c. 300 – c. 360 AD) was originally an advocate from Syracuse, but abandoned law in order to dedicate himself to the composition of his own writings, as he himself attests at the start of the fourth book of his astrological treatise, the Mathesis (4. pr. 1-3). It seems likely that Lollianus Mavortius, the dedicatee of the work, had in those years secured for Firmicus - who was protected by him - a post as court functionary or in some sort of administration, ensuring him the economic security necessary for cultivating the otium he desired (Jones – Martindale - Morris). Until that point, the author remained a pagan, just like his patron; yet following the death of Constantine and the ascension of Constantius II and Constans, when the imperial government began a fierce campaign against pagan cults, Firmicus underwent an abrupt change of heart (Ziegler 1969) and became such a fervent defender of Christianity that, sometime between 343 and 350 AD, he composed a biting apologetic tract, the De errore profanarum religionum. The text presents itself as a discourse given before an imperial audience; it is strongly influenced by Firmicus’ rhetorical-judicial education, especially in its encomiastic and narrative passages. Similarities of language and style existing between this work and the Mathesis have encouraged scholars to accept as virtually certain that Firmicus is the author of both works (Ziegler 1969; Monat). It is likely that the loyalty displayed in the De errore earned Firmicus the appellation vir clarissimus (v.c.) that is found in the manuscripts (Monat). [D. Caso; tr. C. L. Caterine].