There are three common bases for moral reasoning that drive me crazy: capacities, rights, and essences. They bug me because they don’t, and can’t, work even though they dominate the popular discourse. They are different in most ways, but I believe their appeal is what they have in common. I will look at each one in turn before coming to their commonality.
When I say capacities, I’m talking about arguments that rely on, “x thinks,” or “x is sentient,” or “x feels pain,” etc. These are very common in debates around abortion and vegetarianism/veganism, but they show up in other places, too. Pro-choice advocates often point out that a six-week-old fetus doesn’t have a brain yet, so can’t feel pain, think, or suffer. Peter Singer’s famous argument in Animal Liberation relies on non-human animals’ ability to suffer. It comes down to one of two formulations: Entity x has capacity y, therefore x is entitled to the same moral consideration as other entities with the same capacity. Or entity x lacks capacity y, therefore it is not entitled to the same moral consideration as other entities who have that capacity.
On the surface, this seems plausible. There are a few problems with it, though. First, there’s a knowledge problem. When talking about morality, we mostly focus on mental capacities. The problem of other minds comes into play. We simply don’t know what else has the requisite mental capacities. People personify everything they come in contact with. The more like us something appears, the more likely we are to assume it has our capacities, but we can’t know. Maybe trees suffer greatly when we turn them into houses. Maybe lettuce lives a life of torture having its leaves ripped off. Or maybe they don’t. Maybe pigs don’t care that people eat their ribs. Maybe they’re proud and happy to be considered the most delicious animal by many people. Or maybe they hate it. We can’t even always tell if or how badly other adult people who share our language are suffering. Now, this isn’t a serious problem. It’s reasonable to take the precautionary principle to heart. If we have reason to believe that something has a capacity, treat it like it has the capacity. I just bring this up to caution against overconfidence. If someone reads the evidence differently than you, they may not be wrong.
Another problem is that strict adherence to a capacities argument leads to some pretty appalling results. We would lose basic equality. There’s no question that different people have different capacities. If capacities are the basis for morality, we should treat people differently based on their capacities. If a very smart dog attacks a comatose person, does the dog have a higher moral standing because of its superior capacities? Should only those with a certain IQ get to vote? Should we sterilize anyone who lacks the capacity to be a good parent?
There’s also the problem of figuring out which capacities matter and how much they matter. Many Utilitarians focus on the capacity to suffer. Many Deontologists focus on the capacity to reason. Historically, the capacity for language has been huge. There’s no way to pick. Those examples are no better than the ability to wiggle your ears. We could appeal to intuitions or feelings, but, ultimately, whatever capacities we choose are arbitrary.
Next we have to deal with the fact that capacities change over time. If they are the basis of morality, then our moral duties would have to change over time. There are all the normal changes: babies, toddlers, kids, teens, young adults, middle aged adults, and the elderly all have different capacities. Is it permissible to do things to babies and the old that we can’t do to teenagers? If an illness or injury robs someone of a capacity, are they no longer morally relevant? If a brain injury takes away a person’s ability to suffer, is it OK to torture them? If dementia robs someone of the ability to reason, are they expendable?
People who want to use capacities as a base of reasoning try to get around these issues in a couple of ways. One of the most common is to universalize capacities. In others words, they say, “A typical human has this capacity, so we should treat all humans as if they have this capacity.” Another way is to say that, “This being will develop this capacity if we don’t interfere. So, we should act like it already has the capacity.” The problem is that this type of reasoning is itself denying the importance of capacities. In the first instance, it is saying that moral consideration is attached to the species regardless of capacities. The second is making potential the primary carrier of morality.
All this isn’t to say that capacities cannot be used in moral arguments. It is that they cannot be the basis of the moral argument. If someone wants to make the case for veganism, they can’t just say that pigs can suffer. There has to be a further reason why it is wrong to make pigs suffer. If someone wants to justify abortion by saying that a six-week fetus lacks consciousness, they have to explain why it is permissible to kill an unconscious being. Otherwise, the entire morality is nothing more than an appeal to intuition.