Introduced by Ryder in 1970, “speciesism” is defined as a form of discrimination based on species. This concept echoes racism and sexism. First formulated to show the superiority (i.e., the superior rights) that humans attribute to themselves compared to other animals, speciesism then took on board the differences that people attribute to other species. These species differences are based on multiple criteria such as body size, culture, proximity, utility. Whilst we mostly do not like invertebrates compared to vertebrates, we still have preferences inside this taxon, as we love bees but hate wasps. Another instance is based on food culture. It is difficult, and even impossible, for Europeans to eat dogs, yet they eat pork. However, these two species are comparable at multiple levels such as body size, longevity or intelligence. Developing these ideas, Peter Singer questions the consideration humans should give to animals as well as the criteria that could assess whether one species should prevail over another one. Peter Singer stipulated that “all animals are equal”. This is not a factual equality between animals, human included, but an equality based on rights. Indeed, humans are not factual equals among themselves, they differ in several ways, but we treat them in the same way and give them the same rights. Peter Singer is not only talking here about skin color, sexual orientation or cultural difference and body size between humans, he is talking about real human differences, for example handicapped or injured persons. These persons, despite lacking sensory awareness and consciousness, and no longer suffering continue to have the same rights as other humans. Peter Singer then asks why humans should not behave in the same way with other animals.