Do atheists need to believe in God to be moral?

The traditional answer to this is that Christians are not claming that atheists are immoral without God, they are arguing that God must exist for morality to be true. We need an objective source that says that all people have oughts. Without God the oughts are arbitrary. If there is no God then all the oughts come down to reasons like maximising happiness, minimising harm, treating others how you wish to be treated. The problem with this is we are relying on ideas like happiness and altruism are good, and pain is bad. While I generally agree with this, why is this so? If someone else believes that his happiness takes preference over group happiness what can the atheist appeal to? Or who? We are left with people disagreeing.

The moral argument is that if morality is real (not just an arbitrary collection of principles we agree to live by, but can change or abandon) then there is a moral giver. The existence of morality is evidence for God. Consistent atheists realise this and often become nihilists. Though I suspect all men still know that some things are wrong.

Atheists can act morally because they are made in the image of God. Our conscience means that we know there are oughts. This is why the atheist wishes to have a reason for morality: he knows oughts are real, but his worldview denies a deity.

So the Christian argument is that atheism doesn't have an explanation of morality, not that the atheist is immoral. Nevertheless, I think there is reason to suspect that atheists on average are less moral. There are biblical reasons to suspect this, but I wish to raise a more pragmatic one.

Atheist morality frequently reflects the culture (Christians can also be unduly influenced by culture and agree with culture over Scripture). So the atheist call is that they can be just as moral as Christians; moreover, they often argue a superiority because they do not need a deity to tell them not to murder whereas Christians supposedly need God to prevent them killing others.

Of course this is not true. If God gives man his conscience then God is telling the atheist not to murder as much as he tells the Christian. The atheist pretension to superiority backfires as not only does he also require God to tell him right and wrong (by his conscience) he acts immorally by denying his Creator.

But there is a bigger reason the atheist is more immoral? Atheist morality is generally reflective of culture. The Christian thinks that murder and theft and lying are wrong. Atheists will generally agree these things are wrong—we are just as moral as Christians but don't need God! Yet God also condemns many other things. Murder of children is wrong in or out of the womb, sodomy is wrong, government overreach is wrong. Western culture, despite its Christian heritage, by and large has rejected these laws. The atheist who says he is as moral as the Christian because he disapproves of murder and theft is not as moral when it comes to abortion or sodomy. Worse, he condemns the Christian who, despite the culture, recognises these legal actions as sins against God. The Christian is condemned by the atheist as holding to bigoted views that oppress others. Further, the atheist now argues that he is morally superior to the Christian in these areas. But all the atheist has to go on is the spirit of the age. He only has his conscience to bear witness: his conflicting thoughts accuse or even excuse him (Rom 2:15).

So atheists can be moral. The atheist has a conscience that is given to him by God, even while he denies the God who made him. His conscience is somewhat reflective of the culture (or sub-culture) he belongs to and so his morality variably lines up with God's law. And because atheists suppress the knowledge of God many eventually abandon God's law.