This paper analyzes certain restrictions on polarity focus marking in clauses embedded under emotive factive predicates. It argues that these restrictions arise because this configuration leads to a systematic presupposition failure in virtue of its focus value, which I call impossible presupposition. The main argument offered here supporting this approach involves some novel asymmetries with factive clauses in predicate doubling construction in Spanish. From a theoretical perspective, the larger agenda of this article is to provide new evidence that certain types of ungrammaticality are due to semantic-pragmatic factors, namely, logical triviality.