Well, to the original question, I do that almost unconsciously, from a rather early age I learn that how I saw things was different to how others saw them, and taught myself to consider how others would view my actions instead of how they seemed to me. Because of my tendency to do weird things if I keep myself unchecked, And even then sometimes I fail at that.
And about the 100 bill? If I can find the owner then I'd give it back, but if I can't then I don't think the police would do any better. And then, if it's between a random stranger who is not the original owner of the bill and me, I'd just keep it. Then I'd say that to my friends and they would say I'm so lucky and that I should buy them a snack, and so I would.
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To build may have to be the slow and laborious task of years. To destroy can be the thoughtless act of a single day. - Winston Churchill