  Both of these problems are avoided by using Strong Kleene logic (SK) instead. According SK, a sentence with a truth-valueless constituent isn’t automatically deemed truth-valueless. Specifically, a sentence of the form ‘If \(A\) then \(B\)’ (with the conditional interpreted as material) is true if \(A\) is false and \(B\) is truth-valueless, and an existentially quantified sentence is true if it has one true instance (even if some other instances are truth-valueless), and thus neither (19) nor (20) would be deemed truth-valueless. However, the SK treatment of category mistakes possibly errs in the other direction, namely by under-predicting infelicity. Consider for example the following: