Who Has Moral Obligations?
One of the problems with which I continually wrestle is how to build a durable, non-theistic system of ethics. There are a lot of questions which theistic systems have an easy time answering but which are really quite hard if you don't have god to point to (see here, for example). Most recently my attention has been captured by a corollary to the perennial question "Why behave ethically?". If we accept, for the sake of argument, that there is a good, non-theistic answer to this question, one which quickly follows on its heels is "Who should behave ethically?".
The religious side, as a general rule, doesn't have any problem here. The usual story is that humanity is exceptional, has a soul, is made in the image of god, etc... that's why humans should be moral. The non-theistic view, on the other hand, generally emphasizes that humanity is just one branch on a whopping-great phylogenetic tree. And yet I suspect that there are very few atheists who will claim that other apes, much less whales or cows, have an obligation to behave in an ethical manner. What is so special about humanity that we alone, out of all the myriad species on this planet, should behave ethically?
It's surprisingly difficult to find anything on this subject. There's a lot of material addressing the question "Why should an atheist be moral?", but most of it is descriptive rather than prescriptive in nature, focused on analyzing the motivations for "moral" behavior in atheists. Some germane quotes:
The sources of
Why should an Atheist be moral, without a god to make him to do so? You may as well ask why he should use his head for something besides a mobile hat rack. Morality is a built-in condition of humanity; the moral tendency exists in just about everyone, barring psychopaths.
And that, luckily enough, leads us to the foundational principle of morality: empathy. Psychopaths lack empathy with their fellow human beings, and cannot be truly said to have a moral impulse.
Atheism Consistent With Morality?:
I, for one, see no reason to believe there are such things. Nor do I think they are an especially useful fiction; the vast majority of people would, I think, behave exactly the same as they do now even if they believed there were no such things as moral facts--they would continue to be guided, as they are now, by their deepest cares and concerns.
Con: Atheists Can Be Moral, Too:
They are as likely, however, to be guided by sentiment, or instinct, in addition to reason. To answer moral questions, questions about ends and not means, a non-believer will consult "his own heart," Bertrand Russell observed. These questions "belong to a realm...of emotion and feeling and desire...a realm which is not that of reason though it should be in no degree contrary to it." Faithlessness can make moral choices harder; it demands an active inner life as well as a capacity for empathy and engagement with the world.
The above statements are undeniably true, and explain why atheists commonly exhibit behaviors recognized as "good" or "moral", but they don't speak to the concept of ethical obligation. Again, why do we expect ethical behavior from a human but not a cow?
Two of the quotes invoke the concept of "empathy", the ability to identify with the experiences of other entities1, but empathy isn't a uniquely human trait. Many (all?) apes exhibit empathy, as do dogs and mice. As befits an evolved behavior it shows a wide range of expression/variation across these different species. Humans can perhaps be classified, on average, as "extremely empathetic" (if such a designation is meaningful at all), but its clear that we're sitting at one end of a spectrum of behavior shared by a number of other species.
Consider, if you will, the practice of premeditated killing among chimpanzees; can these animals be said to be behaving unethically? Assuming that the consensus answer is "no" we're left with the task of defending that answer in some non-arbitrary fashion. At the same time we have to reconcile the (likely conflicting) verdict we'd render for the psychopath from the first quote, someone congenitally lacking in empathy, for similar behavior. The seeming difficulty of doing so suggests that empathy, by itself at least, isn't enough to explain why we perceive humans, and humans alone, as having ethical obligations.
This is more than just idle philosophizing; understanding who has an obligation to behave ethically, and under what circumstances, is an absolute necessity for any non-theistic system of ethics. Most of the attempts I've seen at answering this question boil down to "follow your conscience", which works fine if you're the only person on the planet but not so well if there are other people about. There needs to be some arbitration mechanism for when individual consciences come into conflict, but non-theistic systems don't ever seem to pan out in that regard.
1 To a first approximation; under the hood "empathy" is a somewhat complicated concept.