 In his Perspectiva and related works, Bacon presents his model for a careful and detailed application of mathematics to the study of nature and mind. In imitation of the De aspectibus of Alhacen (Ibn al-Haytham), he provided an application of geometry to vision that within the terms of reference of his times was successful. But he is critical of both Alhacen and Ptolemy. He sees himself as answering some of the optical problems not solved by either author.