 As with the hierarchy solution to the liar paradox, the truth-value gap solution is by many considered to be problematic. The main criticism is that by using a three-valued semantics, one gets an interpreted language which is expressively weak. One cannot, for instance, in any of Kripke’s languages have a predicate expressing the property of being undefined. This is in fact noted by Kripke himself. If a partially interpreted language contained such a predicate, the following strengthened liar sentence within the language could be formulated: “This sentence is either false or undefined”. The strengthened liar sentence is true if and only if false or undefined, so we have a new paradox, called the strengthened liar paradox. The problem with the strengthened liar paradox is known as a revenge problem: Given any solution to the liar, it seems we can come up with a new strengthened paradox, analogous to the liar, that remains unsolved. The idea is that whatever semantic status the purported solution claims the liar sentence to have, if we are allowed freely to refer to this semantic status in the object language, we can generate a new paradox. 