I think there is evidence for morality being discoverable by secular methods, in religion. To make this argument, I will call on God’s justice and the fact that religions call on their followers to modulate the behaviour of the heathens. And that’s kind of it. The argument acts to do away with the common challenge of “why would atheists defend any morality at all?” The answer is that there is something, demonstrable in humans, that compels us to care how others act.
Now, I’ve already argued that the standard what behaviours in others we care about can be discovered through further understanding of wellbeing and in contractarian terms (i.e. what would perfectly rational entities who have no idea what position they would take in society write as a contract for behavior?). But I don’t think this is a uniquely secular philosophy.
If you are religious, why do you care if I kill people? Why do you even care if I kill you? “Because killing is wrong!” you may be rushing to type in the comments. But that doesn’t quite get us to the full answer. If killing is wrong, and I kill a lot of people, you believe in a God with a perfectly just safety net, right? I will receive my just punishment, and upon death the victims also will receive their rewards or punishments. Death leads everyone to God’s justice. Is that not the world the religious person believes in?
And yet, that seems insufficient to the religious person. Religious people want to modulate Earthly behaviour and politics. They want to stop abortion and stem cell research and extramarital sex. It matters to them how I behave, even knowing perfect justice is coming. But why? From a religious perspective, it doesn’t really matter how anyone behaves because all behaviour is met with perfect justice: murder doesn’t really matter, because the murderer’s actions are exacted. No matter what happens, the scales are always balanced. It’s an orgy of nihilism where no one need care how others behave.
But this simply isn’t the world religious people live in. The religious people care how others behave. The reason for this is that they care about people, even though there is no need for them to, knowing that justice will always be served in their narrative. (There also seems to be a certain level of implicit acceptance that God’s justice is not perfect, but actually massively an over reaction ― that actually the scales are not balanced, but massively tipped with infinite Hell for any transgressions. But that’s an aside.)
Take Islamic suicide bombing as a weird example of this. What would Allah care whether I die an infidel now or in 70 years? Why is Allah so willing to give such a reward to martyrs who kill me earlier than nature would have, given Allah is meant to be an infinite and omnitemporal being? The exacting of justice is coming either way, so what is 70 years to a God that exists outside time? In any narrative, does the suicide bomber achieve anything?
Despite the promise of exact justice, religious people care about people. And “religious” is not the important word here; “people” is. People care about people, and some of those people are religious. The simple fact that religious people care to modulate other people’s behaviour, given a promise of exacting justice, is evidence that the religion and the promise of justice are exactly not the point. The point is entirely about people.
And that’s where we start to talk about the definition of morality. Finding a sociopath who does not care about other people is irrelevant. Taking a contractarian view, morality is about what perfectly rational entities who have a stake in a civilisation would write as a contract of behaviour. People who don’t care, who are not rational, or exploits their known position in society only act as evidence that ‘morally’ is not the only way to act. Morality, in some way, relates to compassion. And that is not a religious phenomenon, but a human one. Compassion takes precedent over future justice, as compassion is about experience right now. (That’s not to say that human compassion isn’t overridden with anger sometimes, but we tend to be able to recognise that as distinct and different.)
Religion offers good reasons to be an earthly nihilist, knowing that it doesn’t matter what people do on Earth precisely because it will all be met with justice. Despite that, people care about behaviour precisely because they care. It’s a human phenomenon, not a religious one. So, when a religious person ponders why an atheist cares about morality, it’s because both the atheist and the religious person are getting that moral impulse from the same place.