Systematic attempts to evolve a system of perspective are usually considered to have begun around the fifth century BC in the art of ancient Greece, as part of a developing interest in illusionism allied to theatrical scenery. This was detailed within Aristotle's "Poetics" as "skenographia": using flat panels on a stage to give the illusion of depth. The philosophers Anaxagoras and Democritus worked out geometric theories of perspective for use with "skenographia". Alcibiades had paintings in his house designed using "skenographia", so this art was not confined merely to the stage. Euclid in his "Optics" () argues correctly that the perceived size of an object is not related to its distance from the eye by a simple proportion. In the first-century BC frescoes of the Villa of P. Fannius Synistor, multiple vanishing points are used in a systematic but not fully consistent manner.