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This study aims to outline the history of the categories marking the transformation of natural perspective into artificial perspective, from the Middle Ages up to the Renaissance. In fact, as early as the 13th century — that is long before the numerous Perspectivæ pingendi of 15th century Florentine artists— many treatises with this title were circulating. I seek to explain the terminology employed by Medieval perspective, the heterogeneous origins of these typically scholastic treatises, by bringing out the different theoretical directions of these traditions: neo-Platonic religious metaphysics of light, represented by Robert Grosseteste’s works; epistemology of sense vision, appearances of visual images and their formation in subjective perception; mathematical geometric theories of the rectilinear propagation of light, the first examples of which are found in the more original authors of the 14th century Parisian school (Dominicus de Clavasio, Nicole Oresme, Henry of Langenstein, Blasius of Parma). In this way medieval perspective was becoming a mathematical physical science, or natural perspective. The last pages of this study outline the influence of the Italian version of the mid-15th century derived from the Latin translation of the original of the Arab optics of Alhazen (Ibn al-Haytham, al-Alasan). This is one of the most important sources of the optical work done by the Italian artist Lorenzo Ghisberti (Commentario III). I refer to Alhazen’s De aspectibus, whose most original doctrines suggested the new optical concepts of Blasius of Parma, that was to exert a great influence also on Italian artists, and especially on Leon Battista Alberti.