The issue is this, and many of us perhaps first learned it in CS Lewis: without God there is no foundation for a true morality or ethic. Without God morals crumble into assertions of power or desire or into a social contract, and into the absence of foundations and boundaries.
Peter Singer, an atheist, responds in A Place for Truth: Leading Thinkers Explore Life’s Hardest Questions.
Big questions: Is there any justification for morality if there is no God? What justification can be offered? Is that justification true or just workable/practicable? Is it just utilitarian?
First, he appeals to the Euthyphro argument: something is right only because God will is (or bad because God doesn’t will it). Or, the “good” is independent of God. [It seems something is missed here: classic Christian ethical theory anchors what is good not so much in the will of God as in the nature of God, and this makes “good” not independent but inherent to who God is.]
Second, knowing right and wrong isn’t that easy. Christians are notoriously inconsistent in what they say they know to be right and good and how they live — do the followers of Jesus live out his teachings on poverty and wealth? And they focus on things not in the Gospels. His points is that we don’t need religion to determine what is good: Christians have a Bible but seem to be constructing morals on their own basis.
Third, Christians claim morals are linked to motivation in order to get into heaven. But he finds examples of moral behavior in folks who are not religious, like Bill Gates and Warren Buffett. There is no strong correlation between being religious and being moral. [He’s spitting into the wind on this one; it’s a spectrum.]
I don’t know about you, but I don’t find his argument at all compelling and it is at times the repetition of old canards and dog-eared simplicities.
So he gives an evolutionary theory of morality. We are, Singer claims, social mammals. Observations shows mammals caring for kin and offspring; we find some sense of fairness in other mammals. So our morality evolved, which doesn’t make it right, as he admits.
And we are reasonable mammals: there are survival advantages in being able to reason; we can see our place in the universe etc. This permits us to perceive the Golden Rule, a form of utilitarianism.
So his atheist morality is the Golden Rule: the rule of empathy. Put yourselves in the shoes of others in order to determine what is good.
John Hare responds to Singer, and Singer’s response to Hare is that there are no grounds for morality; living a moral life — of the Golden Rule — brings a greater sense of harmony in this world.