Inherent variability and the obligatory contour principle

English coronal stop deletion is constrained by the preceding segment, so that stops and sibilants favor deletion more than liquids and nonsibilant fricatives. Previous explanations of this constraint (e.g., the sonority hierarchy) have failed to account for the details, but we show that it can be comprehensively treated as a consequence of the obligatory contour principle (OCP). The OCP, introduced to account for a variety of categorical constraints against adjacent identical tones, segments, and so forth, can be generalized as a universal disfavoring of sequences of like features: *[αF] [αF]. Therefore, coronal stop deletion, which targets the set of segments /t, d/ defined by the features [−son, −cont, +cor], is favored when the preceding segment shares any of these features. But this requires adopting the assumption of inherent variability and interpreting the OCP as a probabilistic constraint with cumulative effects (the more shared features, the greater likelihood of deletion). This suggests an attractive theoretical integration of categorical and variable processes in the grammar.