Although John Locke was neither the first nor the last philosopher to address a problem which artists and aestheticians as well as other philosophers constantly must face, he exerted a telling influence on its history. In his Essay he observed, "When we set before our eyes a round globe … it is certain that the idea thereby imprinted in our mind is of a flat circle."¹ According to David Hume, Locke was not alone in thinking that visual perception involves something two-dimensional: "It is commonly allowed by philosophers that all bodies which discover themselves to the eye appear as if painted on a plain surface."²