Leonardo was certainly familiar, and by all the writers of the Renaissance Perspective and Optics were not regarded as distinct sciences. Perspective, indeed, is in its widest application the science of seeing. Although to Leonardo the two sciences were clearly separate, it is not so as to their names; thus we find axioms in Optics under the heading Perspective. According to this arrangement of the materials for the theoretical portion of the libro di pittura propositions in Perspective and in Optics stand side by side or occur alternately. Although this particular chapter deals only with Optics, it is not improbable that the words partirò la presente opera in 3 parti may refer to the same division into three sections which is spoken of in chapters 14 to 17.].
The plan of the book on Painting (14—17).
14.
ON THE THREE BRANCHES OF PERSPECTIVE.
There are three branches of perspective;