Having been involved in many discussions with religionists on the topic of morality, I often hear claims that have no basis in reality. It is particularly annoying when they arrogantly proclaim they hold a monopoly on morality, for example. This is due to their belief that God is the source or the ground of all moral values. Without God, they say, there could be no moral values and no moral behavior. As with their belief in the existence of God, the idea that morality is dependent on God is not consistent with reality.
This belief manifests itself in different ways. For one, there is a common attitude among religionists that atheists are bad people. They are immoral, and they deserve no trust, and should not be allowed to hold any position of responsibility or public office. For many Americans, atheists are the most reviled category of minority groups. And this attitude is based in large part on the their belief that lack of religious belief implies a lack morality.
We see this hateful attitude expressed by religionists every day. For example, this remark made to me:
Oh that's immoral, huh? I didn't know that you had any morals, IMS. You are an atheist. Morality isn't supposed to be a part of it for you. - JBsptfnOf course, this is a trope that simply isn't true. These people are unable or unwilling to observe the reality that atheists are certainly no worse than themselves in terms of adhering to ethical standards. This has been shown in various studies. And if people like JBsptfn were actually interested in knowing whether atheists think there is room for morality in an atheistic world-view, all they need to do is ask any atheist. But let's not let facts get in the way of their ideological beliefs.
A somewhat more sophisticated belief of religionists is that all humans have a shared sense of morality, but it still comes to us from God. Our fundamental moral values are supposedly "written on our hearts" as a reflection of God's law. And this is their explanation for moral behavior in atheists. It's just that atheists don't recognize where it comes from, according to these religionists. So at least these religionists understand that an atheist can be moral without being religious. That's something, I suppose. But they still insist that atheists have no way to explain where their morality comes from. And this notion is due, once again, to the belief that moral values come from God, as the arbiter of what is good and right. Without this grounding in God, there would be no "ethical axioms", and basis to feel any sense of morality.
The first major problem with this view is that it assumes values exist apart from the mind that perceives them. That's a Platonist assumption that is not consistent with naturalism. Values are very much like beliefs. They only exist in the mind. I can say that something has value to me, but I can't say it has value to someone else. That's for others to decide, and it depends on what is important to them. What seems good to me may not seem good to everybody. The idea that there are moral axioms is highly doubtful.
That's not to say that we humans don't share common values derived from our common heritage. We need to live cooperatively in our society as a means of survival, and this has certainly shaped our evolutionary path. It may in fact be fair to say that our fundamental moral values are "written on our hearts" in our genetic code, as a reflection of the history of our struggle to survive. Here is a thoughtful article on the Biological Basis of Morality. But it isn't the entirety of human morality.
We also get many of our moral beliefs and values from the circumstances of our lives. That is to say they are learned. Society provides many of the moral rules that we live by and believe in. And societal values change. What is right and good at one place and time may not be seen in the same light at another place and time. This points out the second major flaw in the religionist's view of God as the ground of morality. If God is the arbiter of good and bad, then why should human morals change along with societal influences? Does God change his mind and write something different on our hearts from time to time? This is something that religionists have no good answer for.
You might hear them say that people, and even whole societies, deviate from God's law. But you will never hear them say that their own moral values deviate from God's law. Take any moral issue about which religious people disagree. On both sides, they will insist that God agrees with them, and not the other. That's exactly what the Hebrews thought when they slaughtered the Canaanites, or when they took slaves. Given that there is still considerable disagreement between religionists over many moral issues, how can they be so arrogant as to think that their own view is the one that God holds? And that's what they all think.
But the naturalist view of morality doesn't suffer from that problem. It recognizes that moral values are human values. As for the question of what grounds those values, I would say that as the religionist believes he is responsible to God to comply with God's law, atheists tend to feel that they have a responsibility to their family and fellow man - to enhance well-being and happiness. Or if not to society, they feel a responsibility to themselves, to make the most of their life according to their own values.
And if you think that this is not a solid basis for grounding your morality, it sure beats grounding it in something that doesn't exist.