To the question for the originality, the critic importance, and the lasting attraction that provokes Bentham's legal and political thought, the author responds attributing them, as it's frequently supposed, to the use that Bentham makes of the principie of utility as critic tool with which he can examine the laws, institutions, practices, and existing beliefs, and suggest measures of reform. However, states that his originality and importance are mainly due to his ontology and his speech philosophy. For doing so, starts describing Bentham's point of views about the ontology and the speech, then shows how the utility principie is derived from its ontology, and finally tries to demonstrate the permanent meaning of his ideas, taking as an example his analysis about politic corruption.