We're all used to morals, aesops, and lessons. There's just no getting around them when it comes to fiction. They're a constant presence from childhood, and it seems natural to use fiction as a way to illustrate a moral concept. This is a combination of two main factors: firstly, "childhood aesops" are used to simplify and illustrate morals that may be too complex for a child to grasp. Secondly, every writer inevitably reflects their viewpoint of the world onto their writing, so in many cases the events of the world will match their political views or philosophical views (subtly or not).
Many of the aspects of "believability" can be traced down to smaller factors influencing the larger whole. Morality is no different, and one of the key points of a "moral" is that it is meant to connect to real life. Many aspects of "unrealistic" concepts are justifiable because they're just there to look cool. This is not the case with most morals: a moral exists to be connected to real life. Of course, that's not always the case (plenty of morals are perfectly applicable only in-universe) but usually if it's identifiable as a moral, then the author intended it to reflect on reality.
Where morals tend to break down is in that applicability. There are several potential reasons for this: a lack of connection to reality, the introduction of mitigating elements, or authorial control. These three concepts form the baseline for what can disrupt or affect a moral, but they all work on basically the same grounds: there is no way for the audience to reasonably apply this moral to their real lives and expect it to work in the same way. The little changes and influences quickly turn a "simple" moral into a moral that requires many additional factors to make sense.
Lack of Connection to Reality
Known on TVTropes as the "Fantastic Aesop", this sort of moral is based on the presence of a factor that isn't present at all in real life, such as magic or time travel. A moral of this kind is only applicable in-universe because of the base fact that whatever allows for that magic has rules existing only in that universe. The lesson cannot be applied outside of the story, not just because it's "unrealistic" but because making a decision involving the lesson is impossible.
For example, take any setting that uses magic. Does that setting have resurrection magic? Has this magic not been used because "that wouldn't be right"? That's this kind of moral lesson. There is technology in-universe, of one kind or another, to do something. The reason that this technology can't be used is vague and "morally centered". There can be some interesting dilemmas if there is a logical backing to that moral justification; for example, using magic in the Warhammer campaign setting is risky, because there might be a backlash and bad things could happen. However, if it's just bad by itself, for no given reason, then it's not enough.
The same is true of any "magic"-based moral, regardless of what it intends to teach. In real life, humans can't use magic. It's just how things are. Trying to make a moral statement about proper magic use has no effect on people in real life because they can't do that anyways. There is a "moral setup" in such a situation (x magic is Good, y magic is Bad) but the situation is so artificial that it doesn't matter. Again, the dilemma can be interesting in-universe if it's internally consistent, but it's not a moral that can actually be related to real life except in the loosest sense of "making a choice between two things".
Introduction of Mitigating Elements
This is a situation where a real-life moral lesson is being taught, but the justification for that moral lesson is outlandish or unlikely enough to make the moral not work. On TVTropes, this is known as a Space Whale Aesop, named after the plot of Star Trek IV. In short, it can be summed up in this way: would the moral work without the addition of a fantastic element to justify it? If not, then it falls under this umbrella.
a woman, and is thus exempt from that particular prophecy.
Now here's the problem: while Eowyn does get a few scenes illustrating her prowess (fighting off the Oliphaunts and various Orcs), this particular example only exists because the prophecy was there to fulfill. It's meant to be uplifting, but the issue is that the prophecy required a woman (or, really, any "non-man") and she was there to be that woman. How applicable is this to our daily lives? You could use her strength as a justification of female soldiers, but when you reached the whole "prophecy" thing, what does that tell us? It essentially renders her characteristics useless, because it stops being about things that exist in real life (strength, determination, courage) and starts being about things that don't (prophecies involving witch-kings).
In short, if any "real lesson" is justified through the use of unrealistic or non-applicable elements, then this is the issue. Why does this exist? Because it's usually more dramatic to show an immediate magical backlash to an action than to realistically try to depict the actual issues. It's one thing if pollution leads to the destruction of valuable resources, it's another if it leads to an ancient evil being unlocked. It's essentially a childish scare tactic, no different than any over-reactionary news bit.
If the issue was defensible, then more plausible scenarios would be perfectly able to encapsulate why something is good or bad. For example, if you wanted to have an anti-pollution message, all you'd have to do is go forward fifty years and show how bad things would be. The potential problem is that things might not be bad enough for the audience to care, which often results in the author or writer exaggerating to try to "make a point".
Another form of mitigating element is a bit of a reversal: an aesop that works "in real life", but not "in-universe". "Chrono Cross" is one example of this. In the game, the humans are chastised for destroying nature even though they live in small villages with little to no major industrialization. In addition, "nature" is represented by a bunch of hostile races that spend an inordinate amount of time trying to kill humans. The aesop might be justifiable in real life, but in the Chrono Cross world it makes no sense because the same elements aren't in play. The reasons why it doesn't make sense are essentially the same (a mismatch of "cause" and "effect"), but the actual lesson only applies to a situation like one present in reality.
A different example is "Final Fantasy Tactics Advance". In FFTA, a magic book teleports the protagonists to the fantasy world of Ivalice. In-universe, this world is just as real as the "real world" is. However, the main character identifies it as "escapist fantasy" because good things happen to the protagonists. His choice, then, is to sever the two realities - potentially destroying Ivalice - on the assumption that escapism is bad. It's perhaps true that escapism is bad in real life, but in this case it's not really escapism, because the world itself is just as real. There are plenty of things he could mention (the risk of death, the fact that he'll never see his mother again, and so on), but he doesn't. He just insists that escapism is bad, and continues trying to destroy the world.
Even if both the subject and the lesson are perfectly realistic or plausible, the basic fact is that the author dictates the events of the story. The previous issues were issues of cause-and-effect, but even if that is intact, there's still a measure of probability that can be manipulated. That is to say, if an action might lead to a negative consequence, the author can still portray it while maintaining a logical chain of events. However, that depiction will not reflect the actual likeliness of an action. TVTropes considers this to be part of the Alternate Aesop Interpretation concept.
Here is the weakness of the aesop, and this applies to the previous categories as well: all you can do in fiction is depict events with a correlational relationship. The author cannot determine the reaction an audience will have to a lesson. However, they will often have a particular agenda that they are trying to push: one viewpoint is "right", the other is "wrong". Therefore, things must be orchestrated in a way that makes it so that the methods of the "right" side lead to success, and the methods of the "wrong" side lead to failure. Think of any show or story with a "cheaters never prosper" lesson: what if they got away with it, as many cheaters do? The lesson goes right down the tubes. Therefore, the lesson focuses on the times when they didn't prosper, and ignores the times they did. This can result in Laser Guided Karma: the actual likeliness of an event is secondary concern to the moral "cause and effect" relationship. A bad deed must be punished, no matter how unlikely it is.
The most obvious example of this I can think of is one quest from Fallout 3. In this quest, the "good" option is to force Diego to marry Angela, no matter how it happens (the default method is through pheremone-based compulsion). There is no room for disagreement here: players who support Diego's entry into the priesthood will find that their viewpoint is literally not supported by the game's morality system, and players who object to the idea of using ant pheremones to allow a woman to date-rape her prospective boyfriend will be similarly shortchanged. It is not a question of reactions or behaviors - the universe has literally decreed "this is a good thing to do" and that's that.
An alternative system to this is a faction-based system, such as one used by the "Way of the Samurai" series, the "S.T.A.L.K.E.R." series, or in the development kit for "Neverwinter Nights". In this system, there is no morality per se - but there are reactions. If you do jobs for a faction and help them out, they will like you more. If you hurt them, or help their enemies, they will dislike you. In Way of the Samurai 3, helping a faction would result in members cheerfully greeting you as you passed, and their dialogue reflecting a more positive opinion of you. Harming a faction would result in some members attacking you and other members fleeing at the sight of you. This is a logical system based on reputation: people like or don't like you because they know what to expect from you. In addition, you can support a viewpoint that you agree with without it being "right" or "wrong". Instead, the game makes no value judgments and allows you to do what you believe is correct.
The Neutral Story
To me, a good, believable story does not exist with the meta-influences of "aesops" and "morals". If you set out to influence the audience, your story is going to be slanted. I prefer a story where things happen naturally, and based on those logical events the audience can make their own judgments. For example, you can prove that smoking is unhealthy in many ways, but if you want to prove this to an audience you shouldn't have to exaggerate. On the other hand, if they weigh the risks and rewards of smoking, and say "well, I'd rather smoke than not smoke", then there's not much you can do about it - it's their decision.
This is connected to what is known as the "Death of the Author". This is a phenomenon where the intentions of the author become less relevant because of the role of the audience's interpretation. To put it simply, I support this view. An author influencing their work and shaping it to have the outcome they desire is not something that should be considered positive, at least when it comes to learning a lesson about the subject. Every part of a story is orchestrated, yes, but when that orchestration becomes overwhelming, the audience ought to be driven away. The value of a lesson should be obvious if the author really thinks it is. If the author decides that things must be exaggerated to make a point, then they should reconsider their own perspective.
The difference between a "good aesop" and a "bad aesop" isn't necessarily that big - it's just that things that would be forgiven for a "good aesop" (protect the environment, be nice to people, and so on) are not forgiven when it comes to a bad aesop. People propagate Aesop's Fables not because they're perfectly constructed logical arguments with no potential weaknesses, but because the values they teach are usually ones that people like. If faulty logic is used in defense of a popular group, then it will be accepted as "just part of the story". If faulty logic is used in defense of an unpopular group, it will be identified and attacked. This, perhaps, can serve as its own lesson about cognitive biases and double standards.
The concept of making an argument that appeals to the audience is ingrained in this blog as much as I can make it. Plenty of "realism arguments" fall flat because they appeal to realism for realism's sake. This is fine for some people, but other people don't care. This is why I've tried to make the articles on this blog as universal as possible - they're connecting to senses and emotions and logic, not just a vague sense of "this ought to make sense". Of course, the actual results of that are up to you to decide.
So, to sum up:
1) Morals cannot be abstracted - the further you remove them from reality, the less applicable they are in real life. This is not because of sensory details, but because of logical trains of thought.
2) An author is in control of a story. This must be remembered when analyzing a moral lesson: things happened because the author wanted them to, nothing more, nothing less. It might be coincidentally plausible, but it is not truly logical.
3) If a moral is "right", then it should stand on its own. Exaggerating to prove a point only establishes insecurity about the value of a course of action.