 Both theories suffer from an apparent inability to handle error. Science frequently teaches us that things are not in reality the way they appear to the senses. The sun, for example, perceptually appears as a small disk rather than the large sphere that it is (Descartes 1641). This perceptual experience cannot involve either the transmission of forms (since the sun doesn’t have those forms), or the “direct pick-up” of objective properties (again, those properties aren’t there to pick up). Nor could we simply be picking up relational properties, like looking small from here, Descartes argues, because I could have the very same perceptual experience in a vivid dream (where even the relational properties are not instantiated) as I do in waking life. Therefore, perceptual appearances must be entirely mental and internal, rather than relational. Insofar as external objects are at all present to the mind, it is only because of these appearances, which thus serve as inner stand-ins, or proxies, for them. As John Locke puts it, 