This book takes the reader on an inspiring journey into the immune system, challenging long-held beliefs about immunity.It examines the immune system under historical, philosophical and biological perspectives.It proposes a new way of understanding immunity that goes beyond the binary opposition between self and non-self. Indeed, we, the livings, are chimeras. Mammals, birds, reptiles or fish, insects, spiders or mollusks, plants or algae, we are all made up of a community of living beings who share their lives in the same 'meta-organism'.If we live together, it is because we need each other to live, and if we can live together, it is because an immune system makes it possible, by adapting us to them and by adapting them to us.From this mutual adaptation a new kind of immunity emerges, dynamic, relational, never acquired, an endless immunity.Immunity that this system makes possible is not perfect, far from it, it is a compromise which does not always prevent disease; sometimes it even causes it.Disease is the cost of immunity. Because what the immune system enables is much more essential than the defense of the organism, it is the very existence of the meta-organism that we are.Immunity is more than a protection; it is a condition of existence. With its didactic structure and accessible style, this book is an essential resource for anyone interested in understanding timmunity and the immune system.It offers different levels of complexity from which the reader can choose, depending on his or her background, without compromising the main message of the text.With a Foreword by Alfred I. Tauber