The view that animals have moral rights is a difficult one to accept because of the widespread assumption that moral rights come as a package: either you have none, or you have them all.
As it seems laughable to suggest that a chimpanzee should enjoy the right to an education, or the right to freedom of expression, then it is assumed that he should not enjoy any right whatsoever.
But it is possible to justify the right of any mammal not to have pain inflicted unnecessarily without also defending their right to vote at the next election.
That is because a chimpanzee can feel pain, and has an interest in not feeling pain, but cannot decide between the domestic policies of rival political parties, and has no interest in doing so. We do not frustrate any of the chimpanzee’s preferences by not allowing him to vote, but we do frustrate his preference to be free from pain if we kick him around for no reason.
From the very origin of the idea of rights and consistently in the development of this idea, the entitlement of an individual to respectful treatment has been justified on the basis of whether the individual has preferences and acts on those preferences.
If the possession of those psychological capacities determines who has rights, shouldn’t we be open to extending rights to non-humans, provided that they can also exercise the same capacities to some extent?
We can describe some animals as agents with preferences: chimpanzees have preferences about what to eat and where to live - although they do not know they do.
On the other hand, we might have no reason to believe that they have plans for the future or beliefs about their own existence. This suggests that they do not have an interest in their continued existence and that there are no grounds to accord to them a right to life.
These considerations, as any other in moral decision-making, should of course be weighed up with other moral considerations before giving rise to decisions or actions.
Should we stop experimenting on primates if that would slow down scientific achievements that could lead to the development of treatment for debilitating diseases? These questions are difficult, because they require us to weigh up the morally relevant interests of individuals who are deserving of careful moral consideration, i.e. the primates used in research and the people awaiting a cure.
Before we can answer questions like this, we need to know more about the case. Would the primates involved in that particular research project be subject to pain? How likely is it that the research project would give rise to a potential breakthrough? Could the experiment involve other species of animals, less sensitive than primates to pain and stress, or could it be done in ways that do not require any animal to suffer?
Although we do not know a lot about the mental life of other animals, we do not need to know a lot about it before we can speculate that they have an interest in avoiding pain. Good evidence comes from their behavioural responses to potentially painful situations and from physiological similarities in pain perception mechanisms between humans and non-humans, especially in other mammals.
This makes it harder for us to justify current human practices involving other animals, where these animals are treated in ways that are likely to cause them considerable pain. Intensive farming and the use of animals in the entertainment industry raise even more pressing ethical questions than the use of animals in biomedical research, because the outcome of these practices has a more tenuous contribution to make to interests that are relevant to our well-being.
In conclusion, some animals can make a moral claim on us not to be inflicted pain, even if it does not make much sense to accord to them the full range of so-called ‘human’ rights. As long as they can be shown to have preferences that have an impact on their well-being, those preferences deserve moral consideration.