Abstract:  Recently there has been a resurgence of interest in an abductive approach to the epistemology of logic. The rough idea would be that different logics represent different theories of the relation of logical consequence, and that we should select among these as we do in other sciences, based on adequacy to the data and possession of theoretical virtues and vices. But what are the vices and virtues in a logical theory? This paper examines one candidate - strength -, distinguishes logical from scientific strength, and argues that logical strength is neither a vice nor a virtue, and that scientific strength - while a virtue - is independent of logical strength.