[Note: This is an expansion of some points in my previous post]
Morality is a fundamental necessity in any society. Everyone has some sort of moral code, however fractured or distorted it might be. But where does it come from? There are, as I have said, three basic options. Morality is either:
1. Private: I decide for myself what is good and bad, recognising that other people construct their own moralities. This is a postmodern option, as in postmodernism absolute truth is unknowable, and therefore nothing can be absolutely true or false, even in the moral sphere. Yet in practice this would break down completely, there can be no basis for making moral judgements of another's actions that is outside of themselves. I once met a man whose sole basis for making moral judgements was sincerity. "To your own self be true", as Ibsen puts it in Peer Gynt (tellingly, the difference between the 'good' philosophy in that play, and the evil of the trolls is concern for others, the troll version is "To your own self be true - and to hell with the rest of the world!"). This man thus concluded that Hitler was morally good, because as far as he could tell, Hitler was always sincere! While it may have some attractions in the abstract, privatised morality is horrible when considered in the concrete. It may sound good when proposed by a French philosopher, but loses its charm when used to defend mass-murder.
2. Social: Morality is a result of society, and society is the final arbiter. This is probably the position held by most people today. It fits well with an evoutionary worldview, allowing us to look down on previous ages as holding to a "less developed morality." It has the advantage over the purely personal view of morality that it governs whole societies, and thus can be the basis of making laws. But it is not without its own problems. Chief among them is that there must be a definition of "society" for it to work. Who is "Society"? The government? Then Anti-Semitism was moral in Nazi Germany. 51% of the population? This is the reason why modern goverments get so bogged down when they try to change the law on certain issues - because there is no working definition of society that they can use. And, in the modern world, with rapid communications, where is the boundary of society? Is it to be found at the national borders or not?
Another pitfall of a social or societal definition of morality is that it logically robs men of the ability to make moral criticisms of society. If enough people think slavery is right, then it is right, and the man who criticises it, he is wrong. Now, very few people actually hold this position consistently - but that is rather my point, that examined carefully a purely societal view of morality breaks down. According to this system, what is right and wrong changes according to time and place.
3. Empirical: This is an attempt to construct a "scientific" morality, based on observation. Natural science, by its very nature, can only observe what is. Here is the pitfall, logically the result of an empirical morality is that "Whatever is, is right." It is in fact subject to the same pitfall as Societal morality, that it robs men of the ability to criticise what is happening, and lacks the control of public outrage that societal morality has. An empirical morality says, "Africans enslave their fellows, therefore we can buy those enslaved African from the Africans who enslaved them, because the system of slavery is." Logically considered an empirical morality is impossible.
4. Transcendental: Morality is determined by an authority outside of man, the creator God, and is true for all people in all places and at all times. Thus if an individual or group depart from this morality, they can be criticised and called back to the transcendent and absolute standard. The standard is not man, man is subject to it. This position is both logically coherent and workable. It has been the basis for law for most of human history.
Of course, we are then left with the question as to which of the competing truth claims of various religions is true. On that matter I am confident that, weighed fairly, the Bible will be proven to be the truth.