 Stevenson proves the formal consistency and completeness of his set of axioms. It should be noted that completeness here is with respect to the language used. Since this is a minor adaptation of standard logic, there is no treatment of tense or modality, some essential elements of Wiggins’s notion of sortal cannot be expressed, e.g., if a sortal F applies to b at one time, then it applies to b at all times at which b exists, and if a sortal F applies to b, then F necessarily applies to b.