The main idea of this passage from "The Wonders of the Invisible World" is that the narrator is proving proof that the said witchcraft that they thought had happened, has happened. The audience is whoever the narrator is trying to persuade. The tone of the passage is of conviction and of what the narrator thought was true. The purpose of the narrator saying this is to show that they were right and they knew that the witchcraft.
The main idea of the passage above from Cotton Mather's "The Wonders of the Invisible World" is to justify the outcome of the trials. Thank you for posting your question. I hope this answer helped you. Let me know if you need more help.