 His knowledge of optics was connected to the handed-down long-standing tradition of the "Kitab al-manazir" ("The Optics"; "De aspectibus") of the Arab polymath Alhazen (Ibn al-Haytham, d. c. 1041), which was mediated by Franciscan optical workshops of the 13th-century "Perspectivae" traditions of scholars such as Roger Bacon, John Peckham and Witelo (similar influences are also traceable in the third commentary of Lorenzo Ghiberti, "Commentario terzo").In both "Della pittura" and "De statua", Alberti stressed that "all steps of learning should be sought from nature.