An Introduction to the Principles of Morals and Legislation by Jeremy Bentham. An Introduction to the Principles of Morals and Legislation is a book by the English philosopher and legal theorist Jeremy Bentham "originally printed in 1780, and first published in 1789." Bentham's "most important theoretical work," it is where Bentham develops his theory of utilitarianism and is the first major book on the topic. Bentham was the first major philosopher to develop and defend a utilitarian theory of ethics. Like John Stuart Mill, whom he greatly influenced, Bentham believed that happiness or pleasure is the only thing that is good for its own sake. He believed that humans, by nature, are motivated exclusively by the desire for pleasure (a view known as psychological hedonism), and that ethically they should seek to maximize pleasure (a view known as "ethical hedonism"). In The Principles of Morals and Legislation, Bentham seeks to determine what a system of laws would look like if it was constructed on a purely utilitarian basis. To that end, Bentham offers painstaking analyses of the various kinds of pleasures and pains, the sources of pleasures and pains, how pleasures and pains should be measured, the morally and legally relevant components of human actions, the negative consequences of harmful acts, types of behavior that are "unmeet" for punishment, and the various classes of offences. The book contains several of Bentham's most best-known quotations. In Chapter 1, "Of the Principle of Utility," Bentham describes how actions are motivated by the desire for pleasure and are right insofar as they create utility or happiness: "Nature has placed mankind under the governance of two sovereign masters, pain and pleasure. It is for them alone to point out what we ought to do, as well as to determine what we shall do."