It is generally considered unethical to break promises. It is not considered unethical to make promises you would have been better off not to make. Yet when a promise is made and then broken, there is little reason in the abstract to suppose that either the past promiser or the present promise breaker made a better choice about what the future person should do.
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For instance suppose a married woman has an affair. Much moral criticism is usually directed at her for having the affair, yet almost none is directed at her earlier self for marrying her husband in the first place.
It’s not that the later woman, who broke the promise, caused more harm than the earlier woman. Both of their acts were needed together to cause the broken promise. The later woman would have been acting just fine if the earlier woman hadn’t done what she did.
I think we direct all criticism to the later women who breaks the promise because it is very useful to be seen as someone who thinks its important to keep promises. It is of little use to be seen as the sort of person who doesn’t make stupid promises, except as far as it suggests we are more likely to keep promises.
This seems to me a clear case of morality being self serving. It serves others too in this case as usual, but the particular form of it is chosen to help its owner. Which is not particularly surprising if you think morality is a bunch of useful behaviours evolved like all our other self serving bits and pieces. However if you think it is more like maths – something which is actually out there, and we have somehow evolved to be able to intuitively appreciate – it is more surprising that it self serving like this.
Meteuphoric 
When you make a promise, you haven’t yet caused any harm. The act of breaking the promise is the proximate cause of the harm. There is nothing necessarily wrong with making a promise.
We would blame the promiser if somehow we knew she never intended to keep the promise. In that case, many would say making the promise in the first place was the wrong thing and breaking it was an afterthought. I would venture to say that most people think making a promise you don’t intend to keep is worse than breaking a promise that you intended to keep but due to changing or extraordinary circumstances you ended up breaking.
Maybe I don’t understand your argument — it seems to me this is like asking, after a pedestrian is run over by a car, why we blame the running over and not the decision to buy the car. Both acquiring a vehicle and piloting it into someone are both necessary. But given that you have a car, running someone over in cold blood is definitely wrong; buying a car, unless your intention all along was vehicular manslaughter, is not wrong.
The analogy would be if the driver bought the car in the knowledge that he was given to bouts of lethally aggressive driving. But even this puts the earlier man in a more indirect position of causation, since his actions only harm anyone through changing the later mans actions. A better analogy would be if the earlier man told someone else that it would be safe to walk in front of his car later, as he would be sure to stop, in the knowledge that later he may not feel that way.
One potential counterexample: scorn is now being heaped on reckless borrowers, not just those who default on their loans.
I think this applies to a deontologist’s conception of morality, but not a utilitarian. Being of the latter type, I struggled with the notion of marriage for decades.
Prospective marrying couples are aware of high divorce rates. Yet, many exchange vows without a contingency plan in the event of a divorce. To me, this seemed delusional at best and grossly negligent at worst. It’s ludicrous, on its face, to promise a set of circumstances 10, 20 or 50 years into the future. I was quite adamant that I would never get married.
But it’s also true that marriages are nothing more than contracts. And long term contracts, in any form (like 50 year land leases) are modified as circumstances change over time. Contracts can also be broken and aggrieved parties are remunerated in proportion to fault or ability to pay. So, in that sense, perhaps a promise is not a guarantee of a future set of circumstances. Rather, a promise is an agreement to put forth a good faith effort to fulfill the set of terms that both parties have agreed upon. If that is true, the early promiser cannot be blamed. Only the latter promiser is blameworthy because the best effort to keep the promise has disappeared in the face of new unforeseen circumstances. That is, all promises were kept at every moment until the moment of infidelity. Only the recent promiser has not kept his promise.
Looking over your morality list, I noticed even though most of the examples rang true for me, a few did not. As people were closer to me in proximity or familiarity, I preferred them, as I expect most people would. However, when the choice between two sets of people were sufficiently far removed from me, I did not opt for the “closer” one. Instead, I opted for a utilitarian solution.
For example:
– people who exist already more than potential people
When I think about public policy in the face of a Malthusian catastrophe, I tend to think of the already living as a lost cause. Instead, I think the more compelling moral argument should be to favor preventing billions of lives that would be born to grinding poverty and misery. Perhaps I can choose to prevent births as the superior moral action because both circumstances are sufficiently removed from my own life. That makes it easier to be dispassionate and focus on saving the most number of lives.
People often do criticize others who buy houses they obviously couldn’t afford, drug addicts who have babies, or men or women who have a track record that says they probably shouldn’t get married the umpteenth time.
One problem is that it’s difficult to gauge sincerity and intent when the contract is being signed, so we reserve the moral judgment until the case is particularly egregious.
On the other hand, violation of the contract is usually easier to assess. Of course, you may even skewing your example about marital infidelity — not all infidelity is easy to assess, and we only criticize the infidelity that gets caught. And presumably those who get caught often *intended* to be caught; not being the sort who like to have their cake and eat it too. So even on the contract breakage side, we’re only censuring the egregious and easy-to-assess violations.
“It is not considered unethical to make promises you would have been better off not to make.”
This is because an unwise promise is simply an internal problem of the promise-maker, *until* they break it, and morality is mostly interpersonal rather than intrapersonal.
People who make a promise are expected to weigh the arguments for and against it such that we can safely assume the promise-maker is better of with the promise at the point she makes it. If this is not the case, she should not give it. This point is also raised in arguments about broken promises, i.e. the critique is addressed to the former promise-maker, judging from my experience.
So, assuming honest intentions, the promise-maker was better of with the promise ex ante. Since the world is uncertain, she may nonetheless be better of without the promise later on, though. But she could only make the best decision based on her expectations of what would happen. How can we criticize this behavior?
What we are criticizing in the broken promise is then the unwillingness to stick to a commitment from which she knew it could make her worse of ex post. This unwillingness results as she is re-thinking her options ex post and deciding against the promise. We criticize the egoistic nature of this behavior. In the end we may want to trust and keep promises since since they may allow us to be jointly better of. The promise-breaker shows he does not deserve trust and is destroying this commitment device. To discourage this behavior we have to criticize it.
In your example the promiser may indeed be innocent of her capability to have an affair. If perfect self-knowledge is a necessary condition we disqualify all promises.
It is socially useful to blame the promise breaker. It distances the act from the actor.
This stance also allows us to forgive transgressors if subsequent acts are lawful.
“Love the sinner, hate the sin.”
Public promises are designed to induce reliance from others, and generally as part of an implicit bargain – in this case, she promised fidelity in order to get the man to marry her. If that was an unwise deal, that’s her business. But when she breaks the deal, it becomes a moral matter. We do not care nearly as much (legally or socially) about promises that were not designed to induce reliance. For example, if I promise I’ll cook myself a delicious meal tonight, no-one cares if I renege. But if I promise I’ll cook you a delicious meal tonight, it’s bad if I renege. This is also why we criticise people who make promises they should know they cannot/will not keep, as others have pointed out.
It also depends on the kind of promise. Marriage is generally held to be an honourable estate, which reinforces our approval of her entering it and disapproval of her breaking it. If she’d promised a murderer that she’d never turn him in, we’d condemn the promise and applaud the breaking of it.
But marriage is not irreversible (in most countries). She could have divorced, then had casual sexual encounters. Progressive societies wouldnt have assigned any blame to her.
The affair itself has many other negative connotations (deceit, promiscuit, etc) beyond promise-breaking.
Bad example.
In the worldview where we have evolved to intuit moral axioms that have some kind of platonic reality, why should it be surprising that they are self-serving? If they were not self-serving, how would the capacity to intuit them have increased the fitness of our ancestors?
We understand the value of being able to credibly make commitments. Promise breaking reduces trust in general and makes it harder for us to work together for common goals.
Both the promise and the violation are required for that harm. But I do think people would think less of someone who made promises they couldn’t expect to keep, or which gratuitously harmed their future selves. But in far mode we usually like the promises and don’t like the violation, so our sympathies usually lie with the person who makes the commitment.
Finally, we have to seem like we value promises otherwise we will not seem trustworthy, so we exaggerate how immoral we think it is to break promises.