A line of reasoning that presents the opposite side of the author's argument is called a Counterclaim.
What is a counterclaim?
A counterclaim is an argument that opposes or challenges a previously stated claim. It is like the other side of a debate, presenting a different perspective or evidence to refute the initial claim.
Counterclaims strengthen an argument by demonstrating critical thinking and considering different viewpoints. They add depth and prevent an argument from becoming one-sided. They also help us analyze information objectively, consider different perspectives, and build stronger arguments.