n Visual system
n Primitive: a book is an object
n Facet: interpreting a given visual pattern
               on the retina as a book
n Physics phenomenology
n Primitive: bigger is stronger
n Facet: larger objects sink (incorrect generalization)
n Facet: when a truck hits a car, the truck exerts
               a bigger force on the car than the car exerts
               on the truck (wrong)