Two doctrines dominate philosophical and psychological discussions of the relationship between action and space perception from the 18th to the early 20th century. The first is that the immediate objects of sight are two-dimensional manifolds of light and color, lacking perceptible extension in depth. The second is that vision must be “educated” by the sense of touch—understood as including both kinaesthesis and proprioceptive position sense—if the former is to acquire its apparent outward, three-dimensional spatial significance. The relevant learning process is associationist: normal vision results when tangible ideas of distance (derived from experiences of unimpeded movement) and solid shape (derived from experiences of contact and differential resistance) are elicited by the visible ideas of light and color with which they have been habitually associated. The widespread acceptance of both doctrines owes much to the influence of George Berkeley’s New Theory of Vision (1709).