The ambition of this article is to provide a phonological account of an intricate pattern of lenition and gemination in Campidanese Sardinian. The data show two things: that a model of phonology needs some way of showing strength and weakness as positional effects and that neither can be reliably understood in phonetic terms. In this analysis, the discovery procedure does not depend on raw phonetic facts, but rather on a rich model of abstract phonological representations. These representations are of two kinds, melodic and prosodic, and they allow for a substance-free phonological analysis of lenition and fortition in Campidanese that is not confronted by the difficulties inherent in surface-oriented approaches.