I think Lin- Manuel's writing will continue to be read in the future. In that sense he could be compared to Shakespeare, but I never really liked Shakespeare, and I think Lin's writing is more relatable, and could still be in the future.
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Paul celebrated Peter's birthday, then two days later, Peter celebrated Paul's birthday. Because both Peter and Paul are males, we must use the possessive pronoun "his" when speaking of either, or in this case, both of them, which started the confusion represented in this example.