Somebody on a discussion forum asked some questions about Christian morality, and I responded. This happened several years ago, but I was just looking for an old post and stumbled on this and thought it might make a good blog post. So here you go.
As you pointed out, the phrase "objective morality" gets tossed around a lot without defining terms. So let me define this phrase first because it can be taken in at least two different ways.
First way:
Morality is what we take to be right and wrong. Objective morality would then be moral conclusions we came to without the influence of bias or prejudice, but rather that we came to through a fair and impartial look at the facts informing our circumstances.
Second way:
Morality is, in fact, what is actually right or wrong. Objective morality would then include moral obligation we would have whether we choose them or not, whether we believed in them or not, whether we approved of them or not, etc. In other words, the moral imperatives would be incumbent on us independently of human sentiment.
When theists use the phrase "objective morality," we are using it in that second sense, not in the first. Since moral obligations do not derive from any human thought or decision, they must come from some source outside of humanity. We believe it comes from God.
So we humans do not invent right and wrong; rather, we recognize right and wrong. Moreover, morality exists independently of the Bible. It is not merely because some imperative is in the Bible that it is therefore wrong as if the Bible made it wrong. Rather, it is wrong already because God forbids it, and the Bible merely records it because it is true. So the Bible recognizes that certain things are true or false, but it doesn't make them true or false.
After all, Adam, Eve, and Cain were punished for their immorality before the Bible was ever written. God punished the world with a flood for their immorality before Moses ever received the law on Mt. Sinai. And other nations who never received the Mosaic Law were still punished for their immorality.
But as far as specifics go, most moral imperatives have prima facie force. That is, they apply in most circumstances but are not without exception. To be objective is not necessarily to be absolute. For example, it's generally wrong to lie to people, but there are circumstances in which lying is the right thing to do. I went into more detail about that on my blog.
http://philochristos.blogspot.com/2006/04/difference-between-moral-objectivism.html
All it takes for objective morality to exist for there to be any action at all in any situation that it would either be wrong to do or wrong not to do regardless of what any human thought. And it's not hard to think of examples.
1. A man who beats his wife with a baseball bat just because she forgot to get Oreos while she was at the store is doing something that is morally wrong.
2. A single man who has sex with the wife of another man is doing something morally wrong.
3. A woman who slips a date rape drug in her dad's drink, then rapes him while he is incapacitated is doing something morally wrong.
Conversely, I have never heard any theist offer a rational explanation as to WHY it can only be objective, when emanating from a deity or a "holy text."
It's because morality consists of imperatives. Moral law is prescriptive. It imposes obligation. It tells people what they must and must not do. Imperatives can only come from persons. If all that existed in all of reality were non-sentient material objects, nothing would be right or wrong. The universe could be thoroughly described merely with "is" statements, but no "ought" statements. Imperatives can only come from one person imposing their will on another person.
People have instituted governments that make laws which are also prescriptive. But no human law can make something that is otherwise wrong become right or vice versa. Even laws can be just or unjust. For example, a law that required parents to sacrifice their firstborn child in a fire would be morally wrong. It would be wrong to make such a law, and it would even be wrong to obey such a law if it were passed. So the moral law has authority over every conceivable human law, and it is the basis upon which human laws can be judged either just or unjust.
So the authority behind the moral law must be personal, absolute, autonomous, and transcendent. No conceivable creature could have such authority, even if there were a superior alien species from another planet. Something like a god would be necessary to ground morality. The fact that the God conceived of by Jews, Christians, Muslims, and even deists is a person who is autonomous and transcendent and responsible for creating everything else that exists makes that sort of God a sufficient source of morality. It is hard to think of anything else that would suffice.
If a moray is "objective," it is static.
That is not true. What gives a moral imperatives their objectivity is that they come from a legitimate authority whether that authority requires the same thing all the time or whether the authority requires different things at different times.
Can any theist state, specifically, which morals are "universal and objective" that cannot be derived outside of the "holy texts?"
A moral does not need to be derived from holy texts before they can be universal and objective. As I said before, it isn't holy texts that make things right or wrong. Holy Texts can only record things. Any authority holy texts have is grounded in God. God would have that same authority whether the holy text existed or not.
In my view, God created us in such a way that we are able, through reflection on our experience, reason, and intuition, to discern between right and wrong. As the Bible puts it, God's law is written on our hearts. While the Bible can clarify things for us in many cases, for the most part, everybody knows right from wrong even if they're ignorant of the Bible.
Once an "objective moral" has been defined, what significance could the phrase "appropriate to the time" possibly have on the objectivity of a moray?
Some moral are stated in broad terms, then applied to specific circumstances. When the circumstances change, so does the appropriate action. On the surface, it may appear as if the moral obligation has changed since at one time, a person should do X, but at another time, they should do Y. But in reality, the reason they should do X at one time, and Y at another time, is because of some broader moral principle that hasn't changed at all.
For example, it might be appropriate to give a person medicine while they are sick, but once that person is no longer sick, it is no longer appropriate to give them medicine. So it isn't as if the moral law changed from "Give medicine" to "Withhold medicine." Rather, the general moral principle in both cases is "Take care of the person's health," and what changed over time was what the person needed to stay healthy.
So time and circumstances can affect the specific moral obligations we have in virtue of more general moral principles. That's where our "reason" comes into play. It isn't as if there's a moral code that specifies every possible situation you could be in. Rather, there are general moral principles we are instinctively aware of, and we have to use our reason to discover how they apply to specific circumstances, which change through time.
Who is the final arbiter of a disagreement between two (individual or groups of) humans regarding the "objective" moray within any holy text?
We have to make a distinction between moral ontology and moral epistemology. Ontologically, the final arbiter of any moral disagreement is God because it is God who determines what is right or wrong. But epistemologically, disagreements have to be settled on the merits of the arguments for and against both sides, and sometimes people never succeed in settling their differences. Catholics, Mormons, and Jehovah's Witnesses have an organizational structure designed to interpret scripture on behalf of everyone else, and they also settle disagreements.