 Russell finds that when he looks at an object such as a table, his perception of the table does not reveal the actual properties of the table but rather a series of sensations that vary in what they present. The character of color sensations change as one moves around a table, sometimes being brown, but in cases of reflected light (say, from a window), giving a sensation of white. The shape of the table appears as a sequence of quadrilaterals; viewed from one end, it appears as a regular trapezoid, and the physically parallel sides yield a sense experience of convergence. Russell argues for the existence of sense data with a version of the Argument from Perceptual Variation, which, for shape, runs as follows (1912 [1997: 10–11]):