Rachels shows that there can be a certain kind of objective truth in ethics (p. 166).
He says that we discover what is morally right by examining the reasons or arguments that can be given on both sides of an issue and that the right thing to do is whatever action can best be supported by facts, evidence, and reason.
While ethics and science are different, he shows that there can be proofs in ethics.
He goes on to show that these arguments terminate in the question of whether certain conduct makes people better off or worse off.
Choose 1 or 2 contemporary controversial moral issues and give your conclusion on that issue and your argument for that conclusion.