Negative Preference Morality
The Golden Rule is the only moral principle that grounds itself in objective observation. The primary three systems of normative ethics: deontology, consequentialism, and virtue ethics, all share the common failure to conclusively answer the question "Why should I care?" when they make claims of how individuals ought to behave. The Golden Rule, however, does not even ask that we care about the principle at all, it simply explains that when we act in a manner toward others that is inconsistent with how we would like to be treated, then we are being hypocritical and unfair.