The Principle of Utility can be regarded as the keystone of the Benthamite ethical and political thought. In fact, it is at the core of Bentham’s two major works Introduction to the Principles of Morals and Legislation and Deontology. At the same time, the question has been raised about its foundation. This paper is aimed at showing that this foundation can be found in the elenctic defense he proposes at the beginning of his Introduction to the Principles of Morals and Legislation.