In every utilitarian approach to ethics, the moral law is based on self-interest. So to evaluate utilitarianism, we'll ask whether self-interest satisfies the conditions of the moral law.

We noted earlier that the moral law must be universal. Would a moral law based on self-interest have this characteristic? No. Interest, by its very nature, is personal. It's nothing more than immediate pleasure, and pleasure varies from one individual to the next. What pleases me may make you unhappy, and, conversely, what distresses me might be a source of great pleasure to you. Some people can't stand mental labor, for example, while others live for it. What's considered pleasurable also varies from one land – and one epoch – to the next. How could we found a universal law to cover something so variable? This objection applies whether we're dealing with forms of utilitarianism that stress quantitative or qualitative pleasures. Epicurus found more charm in tranquil retreat than in the active life of the public forum. But a more active person would find such tranquility intolerable, preferring the excitement of the crowd and the emotions associated with public contests. How can Epicurus claim that his tastes are shared by everyone? He has the tastes he does only because he happens to have a serious disposition, a calm temperament, and a love of peace. But if I'm of a different mind, following his advice will lead me – as I seek my greatest interest – to act differently.

Mill's doctrine is subject to the same objection.