Although this faculty's relation to distance was affirmed by Descartes, George Berkeley correctly believed that knowledge relating to this faculty was distinct from tactile knowledge.
One work that discusses this human ability examines the life of mathematician Nicholas Saunderson to argue that it is one of two things that provide humanity with "reciprocal assistance." In addition to that work by Denis Diderot, a long-running philosophical debate surrounding it was finally resolved empirically by Pawan Sinha, who set up an experiment to examine it. In An Essay Concerning Human Understanding, Locke reproduces a letter written by Molyneux about whether this could be used to distinguish between a cube and a sphere if it was suddenly bestowed upon a human. Although this faculty's relation to distance was affirmed by Descartes, George Berkeley correctly believed that knowledge relating to this faculty was distinct from tactile knowledge. For 10 points, identify this human faculty, which among other things, allows humanity to discern color.
One work that discusses this human ability examines the life of mathematician Nicholas Saunderson to argue that it is one of two things that provide humanity with "reciprocal assistance."
human vision [accept functional equivalents, such as seeing or sight]