 In contrast to the non-truth-functional logics outlined above, several truth-functional non-classical logics have been proposed, and in particular, many-valued logics (see the entry on many-valued logic). Again vagueness is seen as a properly semantic phenomenon, with the attendant indeterminacies providing cases of semantic underdetermination or overdetermination, but truth-functionality is preserved. The approaches vary as regards the number of non-classical truth-values deemed appropriate to model vagueness and defuse the sorites paradox.