Defeasibility in Law*
Giovanni Sartor
Abstract and Keywords
This chapter provides an analysis of defeasible legal reasoning as
argumentation. It first provides a general account of the idea of
defeasibility and introduces the idea of nonmonotonic reasoning. It then
focuses on defeasible argumentation, considering how defeasible
arguments can be constructed and how they can be defeated by rebutting
and undercutting counterarguments. The dialectical interactions of
defeasible arguments are further explored by focusing on reinstatement
and reasoning about priorities. The idea of legal systems as the basis
for argumentation frameworks is then investigated. The rationale for
defeasibility in law is discussed, along with the possibility of using
different approaches, such as revision or probability, to deal with
uncertainty in legal reasoning. Finally, an account is provided of the
emergence of theories of defeasibility in philosophy, logic, and legal
theory.
Keywords: defeasible reasoning, conclusive reasoning, legal reasoning,
legal problem-solving