Peter Singer’s Animal Liberation is thought to be the absolute best vegan book of the animal rights movement, and a trendsetter. Though people discussed animal rights for thousands of years, he put the concept to a philosophical test.
He proves (to a point where no one has found a hole in the validity of his argument) that our society’s choice to eat animals is speciesism, meaning that we are discriminating against other species of animals. He says that our argument that animals are there for us to eat is alarmingly similar to the argument that slaves are there to do our labour in the fields.
One of his main points is that pigs (as an example) are certainly more aware and conscious of their surroundings than a human baby, and more than a mentally challenged child. But it is considered wrong to eat, or experiment on, one this child.
Therefore, shouldn’t it be wrong to do so to a pig? Why not? Because a pig is a pig and a human is a human? Well, that is speciesism.
I can’t list all the reasons for this argument here (it’s a long book), but if you are looking to learn more about why people think it just isn’t right to eat animals, this vegan book is a must read. See if you can find a hole in his rationale.