A square appears deformed when we superimpose to it diverging rays (illustration 3.1); consequently, to the rays is ascribed the cause of deformation. But if we substitute a scalene triangle or a shapeless object for the square, no deformation is perceived (illustrations 3.3 and 3.4). The fact challenges the concept of "form£ in visual perception. Some considerations follow on the concepts of "good form" and "Pragnanz", pointing out problematic aspects of them. 25 figures are added, 21 of which historical in their original form.