[QUOTE=DudleyGarrett]
Ethically it’s wrong to keep the money? That is completely debatable.
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Only if you play fast-and-loose with the definition of “ethical.” The money does not belong to you, and you concede that: “I haven’t sent them a dime, so I have no idea how I actually received a credit.” So the operative ethical principal is that it is wrong to keep things that belong to other people.
On a macro level, we as a society do. On a micro level, the people to whom you’ve directed the question do. On both levels, you will receive a pretty clear response that it is unethical to appropriate goods, services, or money that don’t belong to you. It’s thievery.
Your time and stress may have value. No one has said that they are necessarily worthless. But the $135 you received BY MISTAKE has no relation to the value of your inconvenience. And even if there is an attempt made to value your inconvenience, it is not your right to unilaterally value it and to impose a penalty that YOU decide on by appropriating money you know was sent to you by mistake.
What makes stealing unethical is the inherent dishonesty of it and the fact that it fundamentally undermines the human trust that allows our society to function. If we all went around stealing from each other, then we would not be able to maintain even the minimum level of trust necessary for commerce to function, since neither side would provide goods or service to the other without payment first, out of fear the goods or services would be stolen. Moreover, it is dishonorable to exploit someone else’s mistake for your own gain, allowing themselves to unknowingly do something to their detriment simply because it is to your benefit. That creates a real harm to the other party, and that also violates the social contract that we will not harm each other.
They don’t owe you the money, and there’s nothing debatable about it. A debt that is owed is fixed by both parties, or is provable by one party. You want to TAKE the $135 as a penalty that YOU have assessed or as the value of your inconvenience, against decided unilaterally by you alone. But you have no legal entitlement to the money and, indeed, if you keep it, you are a thief. Period.
You seem to be trying to create some legal or ethical smoke-and-mirrors where none exists. You would be hard-pressed to come up with a more clear-cut example of unethical (and illegal) conduct than someone keeping money they are not entitled to. It’s not a hard question; you only want it to be.