What is the purpose of a counterargument in a persuasive text?

The purpose of a counterargument in a persuasive text is to respectfully address any doubts or objections to the claim.

When you want to persuade someone through an essay, you need to think about what the reader may say to object to your claim, and add it as a counterargument. You need to think in advance in order to find any counterargument to your claim, so as to make your claim stronger.