The issue of moral status has figured prominently in the arguments of moral philosophers during the last few decades. In particular, it has played a major role in arguments regarding our moral obligations towards animals. There is a significant flaw in many of these arguments, regardless of the conclusions they reach. That flaw is their focus on the characteristics of an entity – its capacities, its relationships – without appropriate consideration of the objectives of morality. Failure to consider the objectives of morality when debating the issue of our moral obligations is like debating whether someone would be a good fit for a sport without considering the demands of that particular sport.

To say that an entity has moral status is to say that it has moral significance in its own right and that it is an entity to which moral agents have certain obligations. What capacities are alleged to give an entity moral status? There is no unanimity here, but among the leading contenders are rationality, autonomy, the capacity to reciprocate, self-consciousness, and sentience. Most human beings above a certain age possess all these capacities, so the claim that these capacities entitle an entity to moral status is comfortably consistent with the modern view that all humans have equal moral status and we are morally obliged to treat all our fellow humans in certain ways, such as refraining from killing them, except when necessary to preserve our own existence.

But here is where the notorious argument from marginal cases is deployed by the animal rights advocate. (I use ‘animal rights’ broadly here. Some who argue that animals have substantial moral status would not claim they have ‘rights’ strictly speaking.) In support of the claim that animals have moral status comparable to humans, the animal rights advocate argues as follows: (1) there is no moral significance to membership within a particular species; (2) instead, moral significance depends on the possession of certain capacities; (3) animals, or at least most of them, are sentient, that is, they experience pleasure and pain; (4) some humans, for example infants and those with severe cognitive impairments (the so-called ‘marginal cases’), have capacities similar to some animals while lacking the capacities of most humans, that is, they have sentience, but they lack rationality, the capacity to reciprocate, and self-consciousness, among other capacities; (5) therefore, some animals have morally significant interests similar to those of some humans; and (6) accordingly, we are morally obliged to give the interests of some animals at least as much consideration as we give to infants and those with severe cognitive impairments. Sentience is sufficient for substantial moral status. The implication of this argument is that unless you want to conduct experiments on infants or cage and then kill the severely cognitively disabled for meat, we are obliged to change the way we treat many animals. The interests of animals and the interests of humans should be given equal consideration.

Animal rights advocates, such as Peter Singer, regard this argument as unanswerable. Meanwhile, those reluctant to embrace the conclusion that animals have moral status equivalent to humans have struggled to come up with some morally relevant capacity or characteristic not connected to species membership that would distinguish infants and the severely cognitively disabled from animals. Some such arguments have been ingenious and complex, but philosophers generally have not found any of these arguments compelling.

Another, more promising, tactic has been to reject the implicit premise of the argument from marginal cases that it is only intrinsic capacities that are relevant for moral status. Some philosophers have emphasized the importance of social relations for moral status, in the process suggesting that animals lack equivalent moral status to humans because, to put it simply, they (or, better said, most of them) don't live with us and work with us. They're not part of our community. This argument has substantial force, and, as discussed below, it does point to a necessary condition for moral obligations, but it would not appear to preclude granting at least as much moral status to Fido or Tabby – that is, to companion animals – as is granted to a severely cognitively deficient human housed in an institution. In other words, it does not completely defeat the argument from marginal cases.

The lesson to be learned from these arguments is that if we confine ourselves to looking at the capacities or social relations of humans and animals, we are unlikely to find any property – some capacity or relationship – possessed by infants or the severely cognitively disabled that is not possessed by at least some animals. Of course, infants and the cognitively disabled are humans, and other animals are not, but we cannot rely on species membership as a distinguishing factor without begging the question.

But why should we think moral obligations are based on an entity's capacities? The standard answer is that morality protects interests and an entity must have certain minimal capacities to have any interests worth protecting. A rock doesn't have self-consciousness and can feel neither pain nor pleasure so we can't really speak, except metaphorically, of things going badly or well for a rock. On the other hand, evil or good can happen to humans because they have interests. They use their reason and autonomy to pursue goals, they have needs and desires, and they can feel pleasure and pain. Similarly, the animal rights advocate maintains, sentient animals have interests at least insofar as they have certain needs and can experience pleasure or pain, and these interests are comparable to those of human infants or the severely cognitively disabled.

Here's the thing though: acknowledging that an entity must have interests to meet the threshold for moral status does not imply that we are morally obliged to grant substantial – or any – moral status to that entity. Having interests is a necessary but not sufficient condition for moral status. Moreover, this threshold requirement for moral status does not imply that the level of one's moral status is based on the nature of one's capacities. This is true not just for animals, but also for entities that may have the same capacities as humans, that is, entities which are self-conscious, autonomous, and rational, as well as sentient. This may seem like a radical, if not repugnant, claim, so let's consider a hypothetical that will support this claim.

Specifically, let's consider a scenario similar to one that Stephen Hawking has envisaged, namely, the existence of an alien race – let's call them the Spores – that is implacably hostile to us. Let's imagine that the Spores have similar capacities to us, including all those capacities that moral philosophers have argued entitle someone to moral status, namely rationality, autonomy, self-consciousness, sentience, and so forth. The Spores use their capacities to torture and kill us. They do this in part because they consume us but, as far as we can tell, they also pursue these activities for sport. Their hostility continues over generations, despite repeated efforts by us to suggest we could and should resolve our differences peacefully instead of fighting. Any ‘agreements’ reached with them invariably turn out to be ruses, designed to give them an advantage in our wars. As it turns out, Spores are also difficult to kill. Other than using weapons of mass destruction, the only way to kill Spores is to burn them for over an hour, a process, which as far as we can tell, causes them excruciating pain. Furthermore, pain seems to be the only thing that they fear, so we have learned to take every opportunity to maximize the amount of pain we inflict on them.

Under these circumstances, would we have any moral obligation to the Spores? What possible moral obligation could we have? Clearly, there is no duty to refrain from killing them, deceiving them, or inflicting pain upon them, and certainly no obligation to assist Spores in distress. Quite to the contrary, based on our experience with the Spores, any attempt to seek peace or show compassion threatens our own destruction. If we accept the principle that morality should not be self-defeating, then we have no moral obligation to the Spores, despite the fact that they have capacities similar to human capacities.

Put another way, a necessary condition for including a class of entities in the moral community, whether they are aliens, humans, or non-human animals, is that inclusion of these entities must not be inimical to the interests of the moral community, and this is true regardless of the capacities of these entities. This necessary condition highlights the partial truth behind the claim of some that social relations are critical for moral status. To be included in the moral community, the interests of an entity must not be invariably antagonistic to the interests of those in the moral community.

The Spores hypothetical illustrates the point that we cannot determine what moral obligations we may have towards an entity merely by considering its capacities. Instead of trying to read off our moral obligations from an entity's possession of some capacity, we should take a step back and ask more fundamental questions: What are the objectives of morality? What are we trying to achieve by inculcating moral norms, by praising or condemning certain types of conduct, by fostering certain character traits? Of course, moral norms initially evolved without our having given any conscious thought to the process, but now that we have the institution of morality we can critically examine it and ask: why?

Simplifying greatly, moral norms appear to serve certain purposes. Moral norms, such as the injunctions not to kill others or deprive them of certain goods, to refrain from cruelty, or to provide assistance to those in distress, enable individuals within groups that accept such norms to achieve a more desirable existence, by, among other things, helping to provide more security to these individuals, ameliorating harmful conditions, fostering trust, and, in general, facilitating cooperation in achieving shared or complementary goals. Moral norms enable us to live together, with the benefits derived from communal activity.

A review of human history shows that there is little variation in the core norms embraced by different human societies. Don't kill, don't steal, keep your promises, help others when you can, be compassionate – these are the norms all functioning human societies have followed because they are essential for peaceful and cooperative relationships. The major changes that have taken place in morality have not been so much to the content of our moral norms but to the scope of these norms, that is, to the range of individuals to whom the norms apply. In early human history, the moral community was no larger than one's tribe; only relatively recently has a notion of a global moral community – of universal human rights – gained widespread acceptance.

But we now have a global moral community and most people think this is a good thing. Moral norms are a useful means of fostering collaboration and adjusting disputes, and the wider the scope of the moral community, the better. The alternative to adherence to moral norms is resort to deception and violence, which, although perhaps temporarily effective, have significant costs. Because the moral community serves the interests of most of us, it is not surprising that we try to ensure its continuation by, among other things, emphasizing the importance of human rights. In our contemporary world, it is an accepted part of moral training to teach our children to treat all others fairly, regardless of their race, nationality, or religion.

The incorporation of all humans into the moral community has had an intellectual side effect, however. Illusory moral quandaries arise when we infer from the fact that we consider all humans to have full moral status that there is some property that humans have – their rationality, their self-consciousness, or what have you – that mystically confers on them this status. Hence, we end up with the argument from marginal cases, which maintains that some animals have the same capacities as some humans and, therefore, must have the same status. As already indicated, this inference from capacity to moral status is illicit. Capacities do not dictate moral status. Without this key premise, that is, that capacities are determinative of moral status, the argument from marginal cases collapses.

How far off track the argument from marginal cases veers becomes clear when we consider the status of infants. The argument from marginal cases maintains that although infants are sentient, they lack many adult human capacities and, accordingly, have a status similar to animals. Therefore, the interests of infants and animals must be given equal consideration. This claim fails in two separate, but related ways, and we can see this when we consider the status of infants from the perspective of the objectives of morality.

In times when humans have sufficient resources to sustain themselves, infants are treasured, and the harming of infants is met with outrage and severe moral condemnation. This outrage is justified. One of the principal objectives of morality is to provide some measure of security to the moral community, to ensure its survival. Our children embody our hopes and aspirations and are crucial for the long-term survival of the moral community. Human children ensure our community has a future; animals do not. Only theories of moral status that have a misguided focus on capacities could ignore this fundamental point.

The other way in which the argument from marginal cases fails is in its effort to embarrass us into granting substantial moral status to animals by equating animals with infants and then suggesting we would never treat our infants harshly. But we have. Infanticide among humans in the Neolithic era was far from rare, with perhaps 15–20 per cent of infants being killed. (Some experts have suggested the rate was higher.) The motivation was not the infants’ lack of self-consciousness or autonomy, but rather population control. Infants are crucial for the long-term survival of the moral community, but in times of great scarcity an excess of infants can threaten the short-term viability of the moral community. As stated previously, a necessary condition for an entity's having moral status is that its interests not be fundamentally at odds with the interests of the moral community.

So, from the perspective of the objectives of morality, infants justifiably have much greater status than animals – except when another mouth to feed threatens the community's survival. The wooden application of the view that sentience is sufficient for substantial moral status results in a faulty analysis in both types of situation. Sentience may be relevant to moral status, but it is not determinative.

So where does this leave us with respect to animals? To begin, the nature of our obligations will differ depending on the role they play in our community. With respect to domesticated animals in general, and companion animals in particular, having welcomed them into our community because of the benefits we derive from them, we have become trustees of their well-being and have an obligation to provide nourishment and shelter and to take reasonable measures to protect them from pain and discomfort. (The circumstances under which we may kill some domesticated animals for food is a complicated question beyond the scope of this article, but I would maintain there is no absolute prohibition of this conduct.) Other animals may, by their nature, be our adversaries (think rats) and our obligations to them are negligible. For many other animals, our only obligation is to leave them undisturbed and, in doing so, refrain from cruelty.

Almost everyone agrees we are morally obliged not to treat animals cruelly, but much ink has been spilled, and many keyboards pounded, debating whether our duties in this regard are direct or indirect. In other words, are we obliged to refrain from cruelty because of a duty we owe directly to the animals – which implies we have obligations to them for their own sake – or are animals merely a beneficiary of the duties we owe to fellow humans? Being cruel to animals can make one a cruel person, and that's not a desirable consequence as far as one's fellow humans are concerned.

My response is that this debate has significance outside the philosophy seminar only if one accepts the view that moral status is derived from an entity's capacities. Those who want to maintain that our duties to animals are only indirect are concerned that if they yield on this point, that is, if they concede we have direct duties to animals, then this implies that sentience is sufficient for moral status and we are back to dealing with the argument from marginal cases. On my understanding of how moral status is connected to the objectives of morality, this is a needless worry. For both humans and animals, moral status ultimately is contingent on whether inclusion in the moral community in some way serves the objectives of morality, so our duties towards animals are no more or less indirect than they are to our fellow humans.

Cultivation of the virtue of compassion and eradication of the vice of cruelty serve the interests of the moral community, and this is so whether the compassion or cruelty is directed towards a human or an animal. There is a psychological connection between our attitudes towards our fellow humans and our attitudes towards animals. Empirical evidence supports this. Moreover, the history of morality suggests a connection. Arguably, the greatest revolution in morality was the abolition of slavery – an accepted institution in most human societies for millennia – which got under way in the early 1800s. At the same time, we saw the first legislation against animal cruelty. This was not coincidental. Although some philosophers have maintained that it was the force of impartial reasoning that resulted in these changes, a more significant factor was expansion of the scope of our sympathies. If we do not care for others, if we are not moved by their distress and pain, no lecture on our moral obligations will motivate us to assist them.

To sum up: we have moral obligations towards animals, but these obligations are nowhere near as extensive as some animal rights activists have maintained. Moreover, the view that capacity determines moral status, and, in particular, that sentience entails substantial moral status, although not without superficial plausibility, cannot withstand scrutiny; it also leads us down the path of paradox and moral confusion.

Some may point out that although I've referenced the objectives of morality as a touchstone for determining moral status and the nature of our moral obligations, and have provided a summary of what these objectives are, I have offered no argument justifying these objectives. This is correct, and a valid point. Even if my summary of the objectives of morality as currently practised is factually accurate, this is not the same thing as successfully arguing that morality should have these objectives.

But what's the alternative? What objectives should morality have, other than the ones I have specified? Is the objective of morality to please God? To produce the greatest amount of cheese? For various reasons, these don't seem like attractive alternatives. Some might say the objective of morality is to treat others fairly, or to promote well-being, and I would not necessarily disagree with those descriptions as a shorthand, but ultimately we have to ask why we should treat others fairly or promote well-being and whose rights and well-being should be our concern and to what degree. Unless something like the objectives I have described provides a justification for the constraints imposed by our moral norms, these questions have no satisfactory answer.