Example: Here's a personal one. My family is not very wealthy. I've worked hard for the things I have and none if it is paid for by my parents. They also work hard for what they have and to make ends meet. My parents used their dying computers every single day and since their computer was so old and slow, it slowed down their productivity... not to mention the fact that they shared a 5 single desktop. So, as a gift to them I bought them a MBP last year. When it was delivered, I received two of them. Should I have returned the extra one? The ethical decision would have been to return it. The logical decision would be to keep it, and I don't think a single person would disagree.
Actually, you're totally wrong. I disagree. Entirely. And there are many - likely the majority - that would also disagree.
The family in your example was poor, alright. Lacking both financial strengths and lacking character strengths. I also grew up in a poor family and we were taught that if it wasn't ours, we shouldn't take it. The thing is that I found several times that being honest can somethings pay off. Several times I found bikes when I was a kid - handed them in to the police then after 3-6 months when unclaimed, guess whose bikes they were? Find a wallet with no ID inside? Guess who got to keep the cash - picked it up from the police station myself.
Now, stop the bickering about how unethical or illegal it is/might be to keep something that was incorrectly sent to you (not directed to you specifically trikky -- more so to anyone in the thread saying it's unethical/illegal). Deep down, we all know it may not be ethical or illegal, but honestly, everyone is in different situations and if they are sent something extra by a stroke of luck, it may be beneficial to them to keep it (as it was in my case).
So, imagine this scenario: You pick up your nice laptop and on your way home to go to Starbucks for a coffee. After about a half hour, you leave and say hello to the homeless guy who's walking in while you're on your way out. You realise on your way home that you left your new laptop on the floor at the table you were using in Starbucks. While you're heading back to the store, the homeless guy is walking out the door with a nice new laptop he received by a stroke of luck.
Also, nobody should feel guilty when Apple of all companies, accidentally sends you something you didn't order... As I said before they've got $150 BILLION dollars and no debt. They can stand to "misplace" a laptop.
By your justification, because you can afford to lay down money on a $2000+ laptop, can drink coffee at Starbucks and drive a car, the homeless guy in the previous scenario has just got himself a shiny laptop and you have no claim to it because he's much worse off than you, and it was simply a stroke of luck that you left behind the computer and he found it.
He didn't steal it, you left it and he found it. A stroke of luck. Totally legit, according to your chain of thought.
No, it's not different at all. He found (received) something to which I (and others, and I suspect you as well) don't think he's entitled. Just because he received it through a stroke of luck doesn't mean he's entitled to keep it.