An interesting fact is that (no doubt with a great deal of effort) we can train our senses to interpret the Chaplin mask as it actually is and not in terms of previous biases based on our historical experiences with faces. This is also true, it seems, of our interpretation of abstract concepts such as those used in economics. With regard to the pollution permit problem, my argument was that the reason Coase had so much trouble persuading the Chicagoans of the correctness of his approach to external effects (an approach based on his definition of a resource as a legal right to control others' actions) is that these economists had "pre-classified" the external effects problem as a problem in price theory. Their propensity to pre-classify in this way presumably reflected their experiences as both students, teachers, and researchers in economics. Coase, studying practical problems of business and not general equilibrium models with quantifiable variables, seems to have had weaker experiences with price theory. One assumes that Demsetz was similar. One might reasonably ask how much damage we do to clear thinking in economics by introducing economics with a model of the prices of homogeneous goods in a spaceless environment.where time is, at best, artificial and uncertainty is nonexistent. Could Steve have had this in the back of his mind when he posted the link to the optical illusion video? Pat Gunning