This is a terrific question. Historically, the dominant picture of morality was once one of absolutes. Things were considered either right or wrong, generally by divine decree, with little or no ambiguity. The main thing that changed this conception was a growing awareness that different societies –or the same society in different eras– have had very different moral standards. As an example, I am a Christian, and thus part of a moral tradition that extends back to the ancient Israelites. Yet some of my moral convictions (such as my affirmation of pacifism) are diametrically opposed to some of theirs (i.e. their warlike tendencies).
The recognition that moral judgments change with time and vary from place to place led to moral relativism, the idea that all moral judgments are subjective and contextual. At most, so the reasoning ran, one could be evaluated by his or her own moral standards and convictions. This too, however, seems wrong. Infanticide, cannibalism and slavery have been practiced in many times and places, yet we would hesitate to call them right, even for their own contexts. Similarly there are virtues –generosity, compassion, honor –that seem worthy of universal affirmation.
Observations of this nature led to a third approach to morality, often called the “perennial philosophy”, the idea that there are common moral principles affirmed in all great philosophies, regardless of time and place –such as the “Golden Rule” (“do unto others as you would have them do unto you”), variants of which are found worldwide. The problem with this idea, however, is threefold. First, there is no clear and uncontroversial way of establishing what actually belongs in the perennial philosophy; second, there is a danger of ending up with a washed-out “consensus morality” that offers no real guidance beyond base intuitions; and third, it seems to preclude all possibility of moral progress –the concept that our morals can get better with time.
My own opinion on the matter is that there are both objective and subjective aspects to morality. I think, objectively speaking, that each entity (such as a person or an animal) and each collective (such as a society, a culture, a species) has a “responsibility” to express its own unique existence, yet no less of a responsibility to promote the interests of all other denizens of the universe. From this kind of standpoint, we can even evaluate the morality of creatures very different from ourselves –judging (for example) a mitochondrion, which supports the functioning of almost all earthly life, as morally superior to a virus, which promotes its own interests at the expense of its hosts.
From a subjective point of view, however, it is clear that there is an ample amount of ambiguity and context-dependence inherent in evaluating even these simple criteria. What is the proper balance between self and society, between one’s own interests and the interests of the universe? And how can one know what serves the interests of the universe in the first place?
It is here, I believe, that religion reenters the picture. Religion –with its connection to the infinite –is what gives us the ability to navigate moral issues with confidence. Yet even faith in an unchanging deity does not mean that human societies, which exist in a changing and evolving world, might not experience changing answers to deep moral questions.