A differend is a case of conflict between (at least) two parties, that cannot be equitably resolved for lack of a rule of judgement applicable to both arguments. One side's legitimacy does not imply the other's lack of legitimacy. Applying a single rule of judgement to both in order to settle their differend would wrong at least one of them, and both of them if neither side admits this rule.;The thesis from which this book develops exposes and reveals the differend between the two genres of discourse it is concerned with - pragmatism and law.