An Introduction to the Principles of Morals and Legislation

Bentham's main work of moral and legal theory. It opens by declaring that nature has placed mankind under the governance of two sovereign masters, pain and pleasure, and builds everything on the principle of utility: an action is right in so far as it tends to increase the happiness of those affected. Rival principles, such as asceticism and appeals to sympathy and antipathy, are dismissed as personal feeling in disguise. Bentham lists four sanctions, physical, political, moral and religious, and gives a method for valuing a pleasure or pain by its intensity, duration, certainty, nearness, fruitfulness, purity and extent, later called the felicific calculus. Long chapters analyse intentions, motives and dispositions, and set out when punishment is unjustified: when it is groundless, ineffective, unprofitable or needless. Punishment must be proportioned to the offence. The final chapter contains the famous note on animals: the question is not whether they can reason, but whether they can suffer. Critics object that it neglects rights and the separateness of persons.

It is the founding statement of classical utilitarianism, and its approach to law, punishment and animal suffering still drives debates in ethics and public policy.