I pointed out yesterday that the Golden Rule doesn’t replace the moral precepts, but presupposes them. This limitation is not a defect in the Golden Rule; it merely corrects a possible misunderstanding about what the Rule is for. As excellent as the Rule is, you couldn’t know how to live if you knew the Rule but nothing else.
The same limitation pertains to all proposed summaries of ethics. Consider, for example, the second formula of Kant’s Categorical Imperative: That we must never treat others merely as means to our ends. One does not have to be a Kantian to see that this is very true. But try interpreting the formula without knowing anything else about right and wrong, and see what happens.
Abortion is wrong because the unborn baby is not a means to his mother’s convenience -- but someone who wants an abortion will protest that she is not a “means” to the baby’s survival. Coercing a doctor to assist in suicide is wrong because he is not a means to his patient’s wish to murder himself – but someone who insists on his assistance will reply he is not a “means” to the doctor’s peace of conscience. Public indecency is wrong because the bystander who cannot help seeing it is not a means to the exhibitionist’s self-exposure -- but the exhibitionist will complain that he is not a “means” to the bystander’s purity. In fact, don’t we hear such arguments daily?
These rationalizations are perverse, but they cannot be corrected just by appealing to the Kantian formula. The bare idea of not using others cannot produce a moral code, for only in the light of a moral code can we tell what counts as using others.