What are three things harry learns about the Wizarding world through his conversation with Ron on the train

One of the first things Harry learns about the wizarding world is that it's dangerous to mess with goblins and flat-out mad to try and rob Gringotts, but Voldemort manages to attempt this a few chapters later, offscreen. Then Book 7 rolls around.The high-security vaults are guarded by dragons.

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the rhetoric device being used to persuade the audience is pathos.