I borrowed this one from Teresa Marques' paper "On an argument of Segal’s against singular object-dependent thoughts" (Disputatio, volume II, no. 21, pp. 19-37) although it owes much to John McDowell and Gareth Evans.
Argument Four. Truth-conditional semantics rests on the assumption that the conditions for the truth of a sentence give the sentence’s meaning or significance. But there is no truth evaluable content when reference failure occurs. If there are no truth conditions, then there is no thought-content. Hence, if one’s utterance of a sentence has no truth-conditions, then it also has no truth conditions and therefore also no significance or meaning. Likewise, an utterance of such a sentence fails to express a singular thought.