
This is a common “gotcha” argument that floats around the Internet. Essentially, it posits that under the teachings of a given religion (typically Christianity), there is a source of morality which is absolute. That might be the religion’s holy text, deity, or the religious authorities of that religion. In either case, there is one authoritative source which dictates what is morally correct and not correct for the entire universe from now until eternity.
So, the argument goes, if one is to reject the teachings of this or all religions, as irreligious people do, it necessarily means accepting that morality is inherently relative and that there is no absolute standard for mortality that is universally applicable. Therefore, as the argument goes, since one would have to accept that morality is relative, it can be framed relative to anything or nothing, and therefore there is no act which can be immoral relative to any reference frames in a context without religion. And therefore, nothing can be said to be immoral because whether it is moral is relative.
That’s the end of the argument.
To its credit, there isn’t anything wrong with this argument. But I do believe the argument posits that conclusion to be far worse than it really is. Suppose I am an irreligious person. Why is fornication with roadkill immoral? Well, because I think it is. It makes me feel bad and the reward gained isn’t worth the risk (the embarrassment of being seen in the act or catching some disease from it). Therefore I don’t do it. Is it possible that some person could think that it is moral? Yes, absolutely. But that doesn’t matter, because even if relative to one person’s moral compass an act is moral, doesn’t mean that people in general can’t just collectively reject that perspective and condemn the act as a group. In fact, human societies imposing their views on what is and is not moral relative to their own experience describes pretty much the entirety of human history.





At least for me, it seems that the assumption that there is no absolute source of morality besides religion is correct. Human morality has changed a lot throughout history, and lots of people have tried to dictate morality across borders and across time. The only ones who have succeeded in the slightest are religious leaders.
The argument is generally that one specific religion provides a source of absolute morality. The existence of conflicting religions does not invalidate that. It provides one source of absolute morality, not necessarily the only source of absolute morality. Anyone can claim something is a source of absolute morality. I can claim a magic 8-ball is a source of absolute morality. It does not mean that people will accept it, but I can claim it.