Avoidance of adjacent similar consonants is argued here to be the result of a constraint against adjacent identical (geminate) consonants in cooperation with other active constraints as opposed to, for example, the direct result of some constraint against adjacent similar consonants. The crux of this Cooperative Interaction hypothesis is the crucial dependence of partial identity avoidance on other aspects of the grammar of the language; the fact that a constraint other than the one penalizing geminates must be active has consequences that are independently verified in a case study of English inflectional suffix allomorphy.