Miguel de Unamuno wanted the readers of some of his novels and plays to seriously doubt whether they are fictitious characters, for such a doubt should lead them to fervently crave for immortality. In this article, I argue that, even though the doubt raised by Unamuno is unintelligible from a grammatical standpoint, it may at least be vaguely imagined, which is just what he needs in order to maintain a vicious circle generating faith that allows us to understand the purpose of his work and, by extension, to try to fill the reader’s life with meaning.