Answer:
He was arrested because he won't reveal the witness that claims to have heard Thomas Putnam admitting that he was accusing his neighbors of witchcraft so that he could swoop in and buy their land.
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The tone of the essay "A Modest Proposal" on a literal level is observant and objective. Throughout the essay, Swift shows the readers what he had observe of the poor people in an objective manner. Hence the observant and objective tone. In a satirical level, it denotes a pleading tone. Swift is proposing a solution to what he had observed and therefore pleaded with the people who can carry out his proposal.