This article presents a unified theory of polarity-sensitive items (PSIs) based on the notion of domain widening. PSIs include negative polarity items (like Italian mai 'ever'), universal free choice items (like Italian qualunque 'any/whatever'), and existential free choice items (like Italian uno qualunque 'a whatever'). The proposal is based on a "recursive," grammatically driven approach to scalar implicatures that breaks with the traditional view that scalar implicatures arise via postgrammatical pragmatic processes. The main claim is that scalar items optionally activate scalar alternatives that, when activated, are then recursively factored into meaning via an alternative sensitive operator similar to only. PSIs obligatorily activate domain alternatives that are factored into meaning in much the same way.