If one is committed to an ethical framework involving some element of moral consideration for non-human animals (henceforth animals), it begs the question of the commensurability of different species. Further, it begs the question of the relative weighting of human lives versus animal lives. How many, if any amount, of animal lives, is equivalent to one human life? I do not propose to definitively answer this question, but rather to highlight the implications of adopting a rights-based approach to the moral consideration of animals, and consider possible obstacles to finding an answer to the above question.

Consider the classical trolley problem – a trolley is moving towards five people on a track, you, standing beside the track, have the ability to flip the direction and the trolley will instead hit (and kill) one person, rather than five. What ought you to do? To begin, let us substitute the five persons for five animals with the strongest claim to a right to life (the West may be predisposed to domesticated animals like dogs or cat, but I offer no objective claim to which animal has the strongest claim). Ought you redirect the trolley to kill one human rather than five animals?

It is important to view this through the framework of rights, in which animals are right-bearers. If one rejects this presupposition, the problem is no longer philosophically interesting and the correct response is (likely) to hit and kill the five animals. However, if we accept that the animals hold a strong claim to a right to life, how ought we balance this against a human’s claim to a right to life?

The important question here seems to be the strength of the animal’s right to life, versus the strength of the human’s right to life. What possibly determines the strength of the right to life? Possible answers include sentience, ability to prospect one’s future life, conscious interest in future life, richness of mental states or some combination of these types of things, to name a few. Is it possible to make this sort of comparison of the strength of claims to the right to life? Intuitively it seems so, as I am of the opinion that a young child has a stronger claim than an elderly person to a right to life (if a situation presented itself in which one had to choose). However, the grounds on which to weigh the strength of these claims is to me entirely unclear, aside from my intuition.

Intuition leads me to believe that the way to weigh the strength of these claims to a right to life is some combination of the pain the death causes and the conscious interest in future life (which seems strongly related to the richness of mental states and ability to prospect one’s future life). In this situation, I conjecture that the pain is equal in either the human case, so that seems to weigh in favour of saving the five animals. However, humans seem to have a greater interest in continued life. This is a hard claim to verify due to the epistemological issues that arise when considering cross-species comparison (it is likely that we can never know what exactly another animal’s mental states are). Despite this, due to the way humans conduct their lives (with much more focus on the future, compared to the present), compared to animals (largely in-the-moment, with a minimal amount of future planning), it seems reasonable to accept that humans have a greater interest in future life.

However, the above solution does not seem to indicate a clear answer to the question of who ought to be saved in the animal trolley problem. Sure, humans have the increased interest in future life. But, how does this singular higher interest compare to the five lower interests of the animals, in combination with their greater pain experienced? This question seems to be largely answerable, as the degree of specificity necessary to be able to weigh the respective interests in future life seems impossible to achieve. Again leaning to intuition, I propose that the right answer (if I had to choose) would be to save the five animals. This is likely counter-intuitive to many (especially non-vegans and non-animal rights advocates), but given the presumptions highlighted earlier, as well as the lack of information necessary to make a fully informed decision, the prima facie case seems to be for the greater number, that is, saving five animals in lieu of one human.

So, it seems that there are an incredible amount of stones to step across en route to a potential definitive answer to the animal trolley problem. There exist epistemological barriers as well as issues of commensurability between the rights of animals and non-human animals. These are surely difficult questions to answer and there exists no easy solution. However, with these barriers highlighted as well as a certain set of presuppositions, the prima facie case does seem to be to save the greater number, until (unless?) a more informed decision is possible.