In phonology, constraints are finally coming into their own. There is no real consensus, however, about how constraints behave, and specifically how they interact with other aspects of the phonology and with each other. Theories of Declarative Phonology (DP) approach this “Interaction Problem” (Scobbie 1991a) in a radical way. In DP everything is a constraint — generalizations and lexical entries alike constrain the form of the intended phonological representation (“surface structure”). Moreover, constraints are mutually compatible, indefeasible and are declared non-procedurally. Declarative Phonology is therefore an extremely simple and restrictive type of constraint-based phonology, eschewing constraint conflict, violation and destructive repair. For details of various declarative theories as well as phonological and computational motivation for the declarative paradigm, see Scobbie (1991a) and the other papers in that volume, Bird et al (1993), Bird (1990), Broe (1993), Coleman (1992), Russell (1992), Scobbie (1991b) and Wheeler (1988).