Planning has traditionally considered the public interest as its principal criterion of justification. The notion of the public interest has traditionally provided the raison d'etre for planning. This chapter talks about four views: divergentism, dialogical proceduralism, liberalism and value-pluralism. The dialogical proceduralist perspective – the public interest does not exist as an a priori criterion – appropriately directs attention to the usefulness of real interaction and debate; but if this point is taken to the extreme, such a position becomes open to criticism. The chapter discusses liberalism and value-pluralism which are usually thought to be intrinsically linked. The widely accepted idea seems to be that value-pluralism is a fundamental component of liberalism. The various contemporary liberal perspectives in the sense can be located on a continuum that ranges from the libertarian-liberal to the egalitarian-liberal. A liberal conception of the state simply presupposes a particular idea or version of the public interest.