Argument used by Russell (e.g. Human Knowledge: its Scope and Limits, 1948, p. 172), and other 20th-century writers, to refute naïve realism in the philosophy of perception. When we see the sun, our perceptual state is the result of how the sun was eight minutes ago. The sun might not even exist now; yet we would still be seeing exactly what we are seeing. So what we are seeing cannot be identical with the sun.