The character Augusto Pérez, upon feeling suicidal, visits author Miguel de Unamuno:

”Very well, then. The truth is, my dear Augusto,” I spoke to him the softest of tones, “you can’t kill yourself because you are not alive; and you are not alive—or dead either—because you do not exist.”

“I don’t exist! What do you mean by that?”

“No, you do not exist except as a fictitious entity, a character of fiction. My poor Augusto, you are only a product of my imagination and of the imagination of those of my readers who read this story which I have written of your fictitious adventures and misfortunes. You are nothing more than a personage in a novel, or a nivola, or whatever you choose to call it. Now, then, you know your secret.”

Upon hearing this the poor man continued to look at me for a while with one of those perforating looks that seem to pierce your own gaze and go beyond; presently he glanced for a moment at the portrait in oil which presides over my books, then his colour returned and his breathing became easier, and gradually recovering, he was again master of himself. He rested his elbows on the arm of the sofa opposite me, against which he was leaning; and then with his face in the palms of his hands he looked at me with a smile and he said slowly:

“Listen to me, Don Miguel—it can’t be that you are mistaken, and that what is happening is precisely the contrary of what you think and of what you have told me?”

“And what do you mean by the contrary?” I asked, rather alarmed to see him regaining his self-possession.

“May it not be, my dear Don Miguel,” he continued, “that it is you and not I who are the fictitious entity, the one that does not really exist, who is neither living nor dead? May it not be that you are nothing more than a pretext for bringing my history into the world?”

– From Chapter 31, Mist, Miguel de Unamuno (translated by Warner Fite)