How can atheists adequately account for the law of morality when according to their worldview, nothing exists except material things?

For the most part, atheists believe in a law of morality just like those who believe in a God. But according to the atheist world view where nothing exists but material things, what is the basis for believing in the existence of right and wrong? What are right and wrong? Are right and wrong material things? Are they natural objects in the natural world like flowers and rocks? Can you touch ‘rightness’ and how much does it weigh or how long is it?

If right and wrong are not natural objects in the natural world then what are they? Are they natural properties like the colour blue or the property of smoothness?

Right and wrong exist as standards above the mere preferences and tastes of cultures, societies and individuals. Atheists can not deny that they are universally perceived. But how can they adequately account for them according to their world view which insists that nothing exists except material things?

Christians believe that the laws of morality are non material moral properties that exist in the real world alongside natural objects, but that attach to actions rather than objects. The Christian worldview can account for the laws of morality because this view of the world includes the existence of non material spiritual entities like God, human souls and angels. But how could an atheist say this when he has already committed himself to a world view which essentially says that the natural universe is all there is?

There is absolutely no basis for anything like a moral law in a universe in which nothing exists but material substances. The preconditions for moral law simply do not exist in the naturalist worldview. There is no way to account for them.

For the atheist to be consistent, he must say that right and wrong do not really exist and that they are merely words individuals and societies have adapted to express their preferences. Ethics must therefore be personal and relative, that men and women, families and nations must simply choose for themselves what they will consider ‘right for them’ and ‘wrong for them’.

From “The Godless Delusion” by Patrick Madrid and Kenneth Hensley.