Should we have moral obligations towards zombies? Intuitively, if a toothless, completely senile old woman with vacant eyes threatens to eat your brains, it's not okay to beat her to a pulp with a baseball bat. But if the same old bag turns into a zombie and attacks you, you're permitted, even encouraged, to beat her or burn her or do whatever you want to her (or it). But it seems that there's no ethical difference between the cases. Let's call the first woman Demented Jane and the second Zombie Jane.
One prominent ethical view, Kantianism, is centered around the ideas of rationality, autonomy and freedom. Ethical norms are justified rationally and understanding them requires the capacity to reason. These norms are meant to direct our will and promote good will. But, without entering into details, we can already see that this view doesn't really apply to our puzzling case. Neither Demented Jane nor Zombie Jane enjoy conscious cognition. Their minds are rotten, the light of reason forever extinguished. They have neither good will nor bad will, but lack the very capacity to will anything. It would be strange to say that Zombie Jane wills brains; she desires or wants brains in the way an animal wants to eat and reproduce.
Moreover, the Kantian can't even begin to account for our strong intuition that attacking the old woman is wrong, since she enjoys no autonomy, rationality or freedom. Similarly, it can't explain our sense that we have moral obligations towards non-human animals or the mentally disabled. Since the cultivation of good will is the purpose of ethical norms, these norms can't apply to creatures incapable of good will.
Another popular ethical view, utilitarianism, links the morality of an action to the amount of pleasure and pain it creates. Roughly, a right action leads to pleasure or happiness and diminishes pain. So, it's not okay to beat up Demented Jane because this leads to pain and suffering, but Zombie Jane doesn't feel pain so it might be okay to beat her up. Plus, Zombie Jane's bite could infect you, which is bad. So, it makes sense to avoid the agony of becoming infected by beating Zombie Jane to death.
However, we can easily describe the example in such a way that these differences disappear. What if Demented Jane is so messed up that she doesn't feel physical pain. Pain, after all, is the result of neurons firing in the brain in a certain pattern. We can easily imagine that Demented Jane's nervous system is so ruined that her pain centers aren't firing in response to physical damage. In addition, we can imagine that Zombie Jane isn't infectious or that maybe we wear a suit which protects us from the virus. Then still, our persisting intuition is that we shouldn't beat up Demented Jane and we are permitted to mistreat Zombie Jane.
Someone may object that even if Zombie Jane can't spread the infection, she's still a rotting body. Such decomposition presents health risks in its own right. So maybe keeping Zombie Jane away with a stick and then burning her with a flame thrower is the only prudent thing to do. In response to this critical point we can further change the example. What if Demented Jane starts decomposing? It may be physically impossible that someone is alive and yet decomposing but here we're talking about zombies so such physical constraints are irrelevant. Let's suppose that Demented Jane starts rotting before she actually dies. She maintains some feeble brain activity and some small degree of awareness but her skin turns blue and she begins to bloat and worms crawl out of her mouth when she speaks. I think our reaction in this case would be to put her away in a sealed room rather than destroy her. Similarly, if a group of people present a health risk for us we quarantine them, we don't exterminate them. Why shouldn't we do the same in the case of Zombie Jane?
In contrast to Kantianism and utilitarianism, virtue ethicists judge the moral worth of an action by reference to the moral virtues or vices it displays. In our case, caring for Demented Jane may be a sign of virtues like respect or compassion for her as a person. But we don't have to exercise compassion with respect to zombies because they aren't people. This approach, however, begs the question. Why shouldn't a virtuous person care for both Demented Jane and Zombie Jane? After all, aren't Zombie Jane and Demented Jane the same person? They share the same body. Plus, neither of them shares the memories of Younger Jane. So, demented Jane has no more psychological continuity with Young Jane than Zombie Jane does.
Finally, it might be objected: "But Zombie Jane is dead while demented Jane is still alive. Demented Jane's heart is still beating and she still has some brain activity. But Zombie Jane has neither of those. We have no obligations towards the dead." This is a fair objection, but we can tweak our example so that the intuitions animating it lose their force. Again, we can bracket the laws of nature and imagine that demented Jane's heart stops beating but she still registers some brain activity. Is she alive then? Or, what if she enjoys a moment of lucidly while the electroencephalograph detects no brain activity? She may passionately talk about her past while there are no medical signs of her being alive. After all, these physical criteria for distinguishing the dead from the living are the product of procedural definitions. They are nothing more than conventions used in order to better apply criminal laws. But we don't want our ethics based on such arbitrary conventions.
So, all in all, the issue of zombie rights is connected with a network of other problems about the limits of personhood, what makes us human and the murky distinction between being alive and being dead. While the issue of the moral rights of animals might have seemed crazy at first, now we are more aware and sensitive towards it. Will the same happen to the rights of zombies?