ABSTRACT
THE study of children's own ideas about projective problems, of which this chapter provides the final example, brings to light a paradoxical situation which demonstrates very clearly how geometrical concepts are formed. On the one hand, projective concepts would seem to depend on visual perception and to do no more than record perceptual data in permanent form. Consequently, objects cannot be perceived otherwise than in perspective, according to complex systems of projection and section. Even when objects retain a relatively constant euclidean size as a result of depth perception, vision still remains euclidean and projective at one and the same time. In other words, even while we perceive an object at its real size it nevertheless appears distorted by perspective.
