How does Poe's punctuation emphasize the narrator's unstable mind in "The Tell-Tale Heart"?
To be clear, Poe is not the narrator of this story. The narrator is some young(ish) man who lives with an older man, perhaps his own father, and who has grown obsessed with the older man's "vulture" eye. Poe uses lots of exclamation points throughout the work in order to characterize the narrator as highly volatile and excitable: as someone who does not seem to be quite in control of himself or his feelings or fears.
In the first paragraph, for instance, such an exclamation point occurs after the very first word, "True!", making it seem as though we, the audience, are being shouted at from the start. The narrator goes on to state that his senses are sharper than typical and that he can hear everything that takes place in heaven and on the earth—even some things in hell. "Hearken!" he tells us, and he invites us to hear how calmly he can tell us the story.
In the third paragraph, likewise, the narrator continues to exclaim. He says that he was so good at deceiving the old man and brags about "with what dissimulation [he] went to work!" He explains how he would open the old man's door every night "oh so gently!" He even insists on his thoughtful wisdom, saying, "Ha! would a madman have been so wise as this."
All of these exclamation points, and there are a great many more throughout the rest of the story, show (rather than tell, since the narrator is the main character himself and he thinks he is tranquil) how excitable he is. He insists over and over that he is perfectly calm, but the repeated use of this kind of punctuation lets us know that he is actually volatile and unstable and—though he denies it—quite mad.
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