Because 2-SAT is polynomial. 3-SAT is the smallest "interesting" flavor of the SAT family. Limiting the forms makes some sorts of reasoning easier, but 3-SAT

Because 2-SAT is polynomial. 3-SAT is the smallest "interesting" flavor of the SAT family. Limiting the forms makes some sorts of reasoning easier, but 3-SAT and k-SAT are effectively the same. There are simple ways of inter-converting. ADDED IN EDIT: http://en.wikipedia.org/wiki/2-satisfiability http://en.wikipedia.org/wiki/2-satisfiability