Vegetarianism, and even veganism, are not recent lifestyles in Europe. Indeed, animal ethics and its practical consequences, such as the refusal to hunt, to honor deities with blood sacrifices, and to consume meat and other animal products, are as old as the West itself. We find traces of it among the first Greek philosophers, Empedocles and Pythagoras, at the end of the 6th century BC. Throughout antiquity, the "Pythagorean diet" was passionately advocated and, by contrast, forcefully rejected. These are the types of topics that we will study during this session. We will see that although some arguments put forward by both sides may appear absurd today, others are sophisticated and persuasive and share much in common with contemporary discourses in favor of animal rights.