When the religious talk about absolute moral principles, they are referring to what they call "God's laws." God's laws are absolute, they say, because God is...well God, and whatever God says is absolute, because He says it. This may seem like a circular argument, but it isn't, because it is not presented as an argument at all. To the religious, it is an autoschediastic asserveration. Since you probably do not know what those words mean, you may be tempted to accept on faith that they are true -- that is how faith usually works. At the risk of endangering your faith, I will tell you autoschediastic asserverations are "self-listing truths," which means truths which are obvious, or what the bad philosophers call a priori knowledge.
(Note: A priori knowledge is the kind of knowledge you have without learning anything. It is the kind of knowledge people have if they receive their education in any modern public (government) school.)
The problem with "obvious truths" is they are mostly incorrect. They are not the same thing as "common sense" which, as a matter of fact, should make us very suspicious of any so-called "obvious truths," especially those that contradict plain facts. Take, for example, the so called "obvious truth" that whatever God says is absolute.
Since absolute means always true under all conditions, irrespective of anyone's wish or will nothing that depends on any authority's choice or declaration, whether that authority is a human or a god, is absolute. Anything that depends on anyone's whim, choice, or declaration is arbitrary and contingent. All dictated law is arbitrary because a dictator is not bound by any law or principle (else he could not dictate) and may declare, by fiat, anything he chooses. It is also contingent because it is not determined facts, but the whim or mood of the dictator at the moment the declaration is made and, of course, the dictator is free to change the "law" whenever a new whim or mood strikes him. Anyone who knows much about the history of religion, particular the Judaeo/Christian varieties, knows God frequently changes His mind -- which means His absolute laws are only absolute temporarily.
True moral principles are neither arbitrary (dictated or pronounced by the fiat) nor contingent (dependent on any agencies, whims, or moods). Moral principles, like all truth, are determined by the nature of reality itself; and, like all truth, are discovered, not decided or chosen by anyone, not even God.
Those who claim there are no objectively discoverable moral values mean they have not discovered any. Human beings have a specific nature and live in a world of a specific nature and it is these facts that determine the moral principles by which human beings must conduct their lives to live successfully and happily in this world.
The moral systems of the religions all consist of moral codes which are nothing more than lists of prescriptions (things we must do) and proscriptions (things we must not do). While many of the things on these lists are things a moral individual would observe, no moral code can possibly be a good ethical system for at least three reasons:
Except for two of the ten commandments, all are prohibitions, that is, "thou shalt nots." Of the two that are not prohibitions, almost no one keeps the first, "remember the sabbath day, to keep it holy,"; and the second, "honour thy father and thy mother," while loosely observed, is not even possible to many people, whose parents have passed away or who, for various reasons, have no idea in the world who their mother and father are. It is odd that an absolute moral code would include a requirement that, at least for some people, is not only impossible to keep, but totally without meaning.
Another odd thing about the ten commandments is that there are not ten. In addition to the two "thou shalts" there are seven "thou shalt nots" summarized as follows: thou shalt not (1) kill, (2) steal, (3) lie, (4) make up your own religion, (5) fornicate, (6) covet, or (7) swear. But seven "thou shalt nots" plus two "thou shalts" only add up to nine. To get ten you must either turn the "make up your own religion" commandment into two, "have no other gods," and "make no graven images," as the Protestants do, or turn the "covet" commandment into two, "do not covet your neighbors house" and "do not covet your neighbor's wife," as the Catholics do. There really are only nine commandments, but ten seems much more impressive and significant, so why worry about exact truth when we're talking about God and absolute moral principles?
These nine commandments, passed off as ten, are touted as the source and foundation of all Western civilization and the moral code that made America what it is today. One would expect anything responsible for so much would be very profound. When we examine these "ten" commandments, however, particularly the prohibitive commandments (you shouldn't kill, steal, lie, make up your own religion, fornicate, covet, or swear) there is not one profound thought among them.
They might seem profound to some aboriginal tribe in some backwater third-world nation, but to those who have spent their lives wrestling with moral issues in a modern advanced country like the United States, the assertion that murder, theft, and promiscuity are wrong are hardly earthshaking revelations. They are such simple concepts they are assumed everywhere there is civilization and intelligence. Even though they are regularly violated, their violation is always "justified" by some supposed "political necessity" allowed in the name of some kind of "rights" or excused as some kind of social or psychological "necessity" (they can't help it), and the justification is always vehemently argued. Even in their violation, their validity is admitted, else there would be no attempt to justify their violation. There is really nothing particularly profound about them.
As for the other two prohibitions, do not covet or swear, far from being profound they are inane. To covet something only means to desire something which belongs to someone else. A desire itself cannot be immoral, even a desire, that if fulfilled, would be immoral. A wrong desire is only a temptation. What virtue is there in not doing wrong if one is never tempted to do wrong in the first place? So long as one only desires what another has, and neither murders them to get it, or steals it in some other way, there is nothing immoral in the desire. There is frequently a perfectly moral way to acquire the desired object anyway.
Coveting is not only moral it is an absolute necessity to the economy of a free society. If no one ever "coveted" anything there could be no economy as we know it, or any other kind of economy for that matter. The local grocery, hardware, or drug store owners are our neighbors. If none of us ever coveted what is their property we would never go to their stores to purchase anything. It is only because we covet our neighbor's food (in his grocery store) or our neighbor's lawn mower (in his hardware store) or our neighbor's medicine (in his drug store) that we go to their stores and purchase the things we covet.
Nevertheless, those who accept the ten commandments as an absolute moral code will swear that it is wrong to covet. They will also explain to you that the ten commandments do not prohibit what we normally call "swearing," only taking God's name in vain is prohibited. What they will not explain is what that means, because they are very likely to have a bumper sticker that reads "God is my co-pilot," and see nothing vain in that use of God's name. We are left wondering what in God's name they mean by swearing.
Maybe the most peculiar thing of all about the ten commandments is that those who insist most vehemently they are absolute do not themselves regard them as absolute. If the commandments are absolute it would be no more immoral to break one of the commandments than another.
In the United States this was, at one time, taken quite seriously. It was felt the dictum to observe the Sabbath was just as important as the prohibition against stealing. In most places "blue laws" were passed to prevent Sunday (the Christian substitute for the Sabbath) from being desecrated. Today the blue laws are all but gone, and while some Christians do sincerely believe they ought to be brought back, none of them are seeking laws to put people in jail for working on Saturday or Sunday or whatever the latest change to that absolute unchangeable law is.
The point of ethics is to tell us how we ought to live in this world. One of the first things one notices about the ten commandments is, except for the two mentioned, they are all negative. It's fine to tell us what we should not do but the real question of ethics is what should we do? To that question the ten commandments provide no answer.
If you tried to live strictly by the ten commandments the only thing you would be required to do is honor your parents and spend Saturday doing nothing (to keep it holy). The ten commandments do not require you to do anything else, and so long as you never kill anyone, steal, lie, make up your own religion, fornicate, covet, or swear, you are perfectly moral. Of course, you won't be worth a blessed thing to yourself or anyone else in the world and will starve to death if someone else does not undertake to feed you but, according to the ten commandments, those, apparently, are not moral issues.
Perhaps the most blatant contradiction of the absoluteness of the ten commandments is the way Jews and Christians, especially those who truly understand and practice their religions faithfully, live their lives. I do not mean they "break" the commandments, although they observe some more loosely than others. On the contrary, in their day-to-day lives they exhibit a decency, reasonableness, and moral rectitude that is much higher than simply observing the ten commandments would produce. Most are productive, self-supporting, honest, ambitious, responsible, and reasonable people who seek to excel and achieve the highest levels of virtue and accomplishment that they are able. In spite of their outward declaration of a belief in an absolute code they live by an absolute principle that "to do less than your best is a sin."
This is not to be taken as an endorsement of Christianity or any other religion. With extremely few exceptions almost all religionists embrace and promote some form of superstition. Nevertheless, there are degrees of dangerousness in superstition. A Christian of the Reformed branch is much to be preferred to that anti-religious movement called Humanism for example. The Reformed Christians believe their God predestines the majority of mankind to eternal torment in hell but that hell, at least, is in the next world. In this world these same Reformed Christians are great defenders of individual liberty and moral values. The collectivist, statist, altruist, anti-moral, pseudo-intellectual ideology of the Humanists, however, if actually put into practice, would make a hell out of this world, here and now.