Scalar implicature has served as a test case for investigating the nature of inference processes in language comprehension. Specifically, the question of whether or not scalar implicatures are computed by default has been extensively investigated in recent years. We argue that the question of default is overly simplistic and propose instead to think of scalar implicature computation as a problem of optimal cue combination within a constraint-based framework. We provide evidence from three experiments supporting the view that multiple constraints of differing strength operate in parallel to provide probabilistic support for or against an implicature.