For many centuries there have been pleadings to include non-human animals in our moral circle. The blind Syrian poet Al-Ma'arri (973-1058) was probably the most explicit messenger. He condemned the use of milk, honey, eggs, or animal body parts. But why? For a long time black people, women, homosexuals or people with non-binary identities were not part of our moral circle. The reason for their inclusion seems straight forward: they're human beings, just like the white heterosexual man. However, that is not a satisfactory argument. For why does the criterion of being human matter when it comes to morality? One might respond that human beings, in contrast to other animals, can talk or reason. But why would the ability to talk or reason matter morally? Why would we have to protect a person that can reason? Maybe because reasoning can lead to ideas or personal development. But again, why would that matter to us?

In the 18th century Jeremy Bentham pointed out: “the question is not, Can they reason? nor, Can they talk? but, Can they suffer?" (p.311, as part of footnote 1). Since no one rationally wants to suffer, unnecessary suffering is what our moral thinking has to prevent. Following this, our moral circle should include every being that can suffer, every being that is sentient. As far as our current knowledge reaches, most animal species have the ability to suffer. However, this ability is disputed regarding some species. We have to act based on provisional knowledge and should be willing to adjust that knowledge through the process of falsification without causing unnecessary harm. For now, since most species are sentient, we have to act precautiously. Should we assume wrongly that a certain species is sentient, not much damage is done. The other way around is obviously problematic.

In the 1970s, philosopher Peter Singer began promoting this view. Following his book Animal Liberation the vegan movement grew internationally. In 2001 in the Netherlands, his fellow philosopher Paul Cliteur rightfully pointed out: "if human beings are related to animal beings, then it's no longer self-evident that human beings have rights and animal beings are lawless." (p.26, translation BC.) Among others, cows, pigs, chickens, ducks, fish, dogs and cats have the ability to suffer. Following the conclusion that all sentient beings should be included in our moral circle, the consequences are huge. They should not be imprisoned or abused for the consumption of their products or bodies. Moreover, we should let non-human animals be. Stock breeding and dairy farms will have to be closed permanently. Cow milk will only be for the calf and honey for the bees. Shoes will be made of plants or synthetic material. As Janneke Vink convincingly points out, there is no justification for zoos. Our society will be completely plant based. The only problem is that we are not willing to see this. We are happy with our moral blind spots, so that we don't have to change our habits. In the meanwhile, non-human animals keep being slaughtered and abused. In the Netherlands over 600,000,000 animals are killed for meat production annually. Cliteur believes that the way we treat non-human animals might be the moral blind spot of our generation. He asked the question how future generations will look back at our moral progress. Will they reflect on our thinking and acting in the same way we now judge the slave masters of only a few centuries ago? I'll let you come up with the answer yourself.