I recently attended a debate on this subject, and have been mulling over it ever since.
Why can those who reject religious doctrines, and therefore acknowledge moral relativism (to reject pre-established systems of absolute morality, i.e. religion, is to assume either that one’s own self defined morality is absolute - a rather arrogant and easily delusional assumption - or to acknowledge that there is more than a single answer to every moral question), not hold themselves to decent moral standards?
In fact, I would argue that to practice modern Christianity is to, on some level, acknowledge moral relativism. Modern Christians have a historically unique interpretation of the Bible. Many things once considered biblically ethical to do are no longer considered ethical at all, e.g. slavery, or stoning to death. The fact that there can be interpretations of the Bible at all is a testament to the fact that we as humans can be wrong about morality (it’s happened many times). The fact that morality, even from the Christian perspective, can change, proves that it is not absolute (if morality were absolute, Christianity would be completely unchanged in the past two millennia). This doesn’t mean you can’t be sure about your own morals, only that we all agree: morality is obviously subject to revision.
To be an “ethical” or “moral” person, I think, is to be both rational and compassionate. Without compassion, rationality easily becomes selfish malice. Without reason, even those with the best of intentions can fail to act in a morally responsible way. We see this when parents of sick children pray for healing rather than call an ambulance, and thus sentence their children to death. To be rational and compassionate is to want the best for all while still being pragmatic and open to critical thinking, a foundation from which we can draw many moral lessons such as “treat others the way you would like to be treated” and construe every significant ethical point that we consider absolute in our society, e.g. murder, rape, thievery are wrong.
But where do rationality and compassion come from, if not from God? One of the big arguments in this debate was that without an arbitrary moral authority, morals have no weight beyond the individual and thus cannot be meaningful. If morals are relative, nothing can be considered truly right or wrong and murder can be righteously justified as easily as love.
However I believe reason and compassion have a completely natural and very human foundation. Reason, of course, I think we can agree is an innate property of humans. This has long been cited as the difference between man and animal. Our ability to reason is why we are the dominant species on this planet.
Compassion is less apparent but still makes sense evolutionarily. It absolutely makes sense to have compassion towards other members of one’s species, and thus collaborate constructively towards the survival of that species. Pirañas, for example, are vicious and bloodthirsty when they feed, but they don’t eat each other.
Now, one can hardly call a Piraña a moral agent, but animals demonstrate a higher level of pseudo-compassion as well: for instance take a look at this 1964 study on Rhesus monkeys:
Given a chain to pull that would both dispense food and deliver a painful electric shock to the monkey in the adjacent cell, the study found that a majority of monkeys would starve themselves for days at a time so as not to hurt each other (a higher incidence of this when the monkeys had previously interacted personally).
Now, of course, neither humans nor any other species are necessarily compassionate. That is why there are wars and crimes, and that is not my argument. My point is that to say that an atheist cannot be moral is to say that there is no foundation for reason and compassion outside of religion, which is simply not true.
And to argue that religion is the determining factor in morality is simply not true either. There are plenty of faithful people who demonstrate an utter disregard for moral “truths”, and furthermore many who murder, rape and pillage * because * of their faith. In fact, I would argue that a person’s faith and how ethical they are have no correlation at all.