*Me breaking up fight*
6yo: -But he hit me!
Me: Because YOU hit HIM! Look, long ago it was an eye for an eye, but do you know what happens? Everyone ends up blind!
6yo: No they don't.
Me: What?
6yo: The first person wins. Other guy can't see, so he can't take the last eye.
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(This is the full size version of this image. Figured it might be a good one for phone backgrounds!) :)