The aim of this paper is to explore the nature of author variants in the humanistic age, starting from a survey of the variants added by Petrarch to his unfinished work Africa during the revision of the text around the mid-fourteenth century. In particular, two new definitions of variant, which were presented in a previous paper, are here outlined and discussed, that is, ‘active variants’ and ‘working variants’. Furthermore, the so-called Scevola Mariotti’s norm in relation to the author variants’ authenticity is reviewed.