Book excerpt: This book by Roberto Esposito - a leading Italian political philosopher - is a highly original exploration of the relationship between human bodies and societies. The original function of law, even before it was codified, was to preserve peaceful cohabitation between people who were exposed to the risk of destructive conflict. Just as the human body's immune system protects the organism from deadly incursions by viruses and other threats, law also ensures the survival of the community in a life-threatening situation. It protects and prolongs life. But the function of law as a form of immunization points to a more disturbing consideration. Like the individual body, the collective body can be immunized from the perceived danger only by allowing a little of what threatens it to enter its protective boundaries. This means that in order to escape the clutches of death, life is forced to incorporate within itself the lethal principle. Starting from this reflection on the nature of immunization, Esposito offers a wide-ranging analysis of contemporary biopolitics. Never more than at present has the demand for immunization come to characterize all aspects of our existence. The more we feel at risk of being infiltrated and infected by foreign elements, the more the life of the individual and society closes off within its protective boundaries, forcing us to choose between a self-destructive outcome and a more radical alternative based on a new conception of community.