Abstract: This article was written for the 2005 Symposium: "Calabresi's Costs of Accidents: A Generation of Impact on Law and Scholarship" held at the University of Maryland Law School. Donald Gifford provided the following summary in his introduction to the symposium issue: Adam Benforado and Professor Jon Hanson analyze Calabresi's and Posner's very different views of law and economics using concepts borrowed from social psychology. They view Posner as representative of the "relative" dispositionist whose analysis proceeds from the belief that "[t]he individual is presumed to be an independent, choice-making agent whose acts both satisfy and reveal a set of underlying preferences." In contrast, according to Benforado and Hanson, "Calabresi stands as a relative situationist in a particularly dispositionist school of thought";] he "has the instincts of a social psychologist," and differs from those who would "ignore the more significant role played by situational forces - unseen or underappreciated features in our environment and in our interiors." Benforado and Hanson suggest that both Calabresi's and Posner's intellectual development were influenced greatly by their differing reactions to changing intellectual trends emerging during the 1960s: Calabresi seems to have embraced "the general push toward situationism," while Posner was one of a number of scholars that "lashed back in an attempt to legitimate the systems that were being upended by situationist thinking."