The old “religion is the source of morality” chestnut is one that’s been polished so often by religious and non-religious commentators alike that it’s difficult to find, or to say, anything by either side that hasn’t been said. Nonetheless I shall summarise, in general, the popular arguments as I understand them, and elaborate on the one that appears the most plausible.
Religionists, usually theistic, proclaim that their god/s handed codes of decent behaviour to humanity; they often refer to a universal, common or even “absolute” morality among human societies, the existence of which can not be explained by any natural means. A common scriptural narrative is that humankind was created perfect, sin-free (often in their gods’ image) and then rebelled (or were corrupted), bringing evil into the world which necessitated divine instruction on behaviour. Scriptures spell out precisely what we should and, very importantly, should not do and often promise reward or punishment as the particular behaviour warrants.
The reason given for the world not being a writhing morass of hedonistic lubriciousness and brutality is that our benevolent god/s have told us that such things are unacceptable if we want to attain post-mortem paradise. People who assert no religious belief but who behave morally are either lying to themselves or others and are actually religious, or are simply taking advantage of the extant religious moral code without giving proper credit to the god/s in question for imposing it in the first place. These self-described non-religious people, if genuine
Non-religionists or naturalists will counter simply by saying that they base their behaviour on how it affects others; that they are using their advanced human cognition to build on innate empathy and consideration for fellow beings; that considerate behaviour is not unique to humanity and many social organisms (not just the well-known examples of our primate & mammal cousins but fish, birds, ants & colonial microorganisms) display cooperative tendencies that benefit their group’s survival. It’s asserted that behaviour that benefits a group is so easy to discern and so conducive to survival that it very frequently occurs unconsciously and as such may even be passed on, at least in part, genetically (hence its prevalence); that it is a simple, undeniable, easily observed fact of nature that a group which cooperates in finding resources & providing protection will be more likely to survive & thrive, giving its members more opportunities to reproduce.
They may also mention that universal or “absolute” morality does not actually exist, as evidenced by the fact that cultures across the world and throughout history have developed innumerable disparate & even contradictory versions of what is moral & ethical (and not always from religious sources); these values have over time not only changed but even been turned completely around (indeed, this is an ongoing process with many countries still debating such things as marriage equality, capital punishment & the legality of narcotics to name but a few). They may further draw attention to the fact that other moral codes & laws existed many, many years before the religion in question even began and that to get to the point of being civilised humans at all, our comparitively less-intelligent ancestors would obviously and necessarily have had to cooperate in many different ways to survive in a world full of mortal dangers. Australopithecines and other ancient hominids, not known for the verbal or philosophical sophistication required to prescribe or codify behavior, obviously survived long enough to breed and spread and have their ancestors diverge genetically to the point where Homo Sapiens arose. This could not have happened were they mindlessly savage & looking out only for themselves as individuals; indeed, it could be persuasively argued that pure selfishness in such times was a sure way to get yourself expelled from a group and greatly increase your chance of ending up as prey. It is a simple & accepted fact of nature that there is safety in numbers. Humans are merely building on that simple fact; our abstract reasoning ability, verbal skills, memories of personal experience & empathy all allow us to exchange experiences, determine potential harm or benefits to certain behaviour & discuss what in fact “should” be considered moral.
I fall into the latter camp, the evidence for the religious explanation (based as it is on an entirely unproven assumption: the existence of ultra-powerful deities with specific desires) being virtually nil. Further, any specific religious argument for a divinely-commanded common, absolute or universal morality is easily dented or cracked wide open by referring to a different or contradictory religious moral code, or to a religious code that has simply changed over time. This can be done while still within the bounds of the faith in question; it’s not necessary to even compare one faith to another. Many religions have suffered schisms and years of unimaginable sectarian violence based on differing opinions of how to interpret the same texts (and some still do). Moral issues have played no small part in these disagreements. Many people point to, for example, the hundreds or thousands of different sects just within Christianity and their sometimes wildly differing moral stances on such questions as homosexuality, divorce, abortion & euthanasia (all curiously related to peoples’ private lives and personal autonomy); I maintain that the exact number of sects, while telling, isn’t that important when talking of absolutes. It’s sufficient to point out that there’s more than one kind of Christianity in order to cast strong doubt on any claim of a “universal” or “absolute” moral code. How can there be anything even close to “absolute” if there’s not even consensus among Christians?
I will not accept that a fractious group of ancient faiths have some monopoly on being kind to others and that without them we would all be awash in hedonistic carnage; indeed, I think such selfish and destructive behaviour would have seen the end of our species before it even began. Morality is not some magic spell handed to man on a silver cloud or carved into tablets; morality is what arises out of necessity from a group of organisms who need to get along or die. We’ve just managed to polish that instinct up a little.