More Than One Quality Today
Although the distinction between affirmation and denial is rarely supported today, you might try to argue that some other distinctions in the structure of assertion could be thought of as differences of logical quality. One might argue, for instance, that the distinction between sequents with empty and non-empty antecedents amounts to a distinction between logical consequences and logical assertions. Alternately one might claim that both forms are really just logical assertions in the metalanguage, and are not statements at all in the object language, since the turnstile isn't in the object language. Similarly you might argue that a modern language which includes both an assertion mechanism, and a "retraction" mechanism (such as Diderik Batens' "Adaptive Logics) could be thought of as having two logical qualities "assertion" and "retraction."
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