Charles W. Morris
According to Lewis, the logical positivists failed to distinguish between "linguistic" meaning - the logical relations among terms, and "empirical" meaning - the relation that expressions must experience. (In Carnap and Charles W. Morris' terminology, empirical meaning falls under pragmatics, while linguistic meaning under semantics.) Lewis argues against the logical positivist who shut their eyes to precisely that which properly confirms a sentence, namely the content of experience.