The handling of objects leads in practice to the analysis of figures, or of shapes. There is…a simultaneous construction both of euclidean figures (as a result of the object being ascribed a constant size), which remains the same during changes of position) and projective figures (as a result of coordinating different views of the object, i.e. perspective) p 10). [objects result from] perceptual constancy of shape and size (p 10)
