to be total strangers (idiom)

You've got a million dollars in front of you. You can either spend it for yourself or spend it on a surgery for someone you don't know who is in danger of quadriplegia. You don't know each other. And no one will ever know what a noble deed you've done sacrificing all the money for the surgery for a person you don't know, or how mean you were to take the money confining that person to a wheelchair for the rest of their life. So what would you do? You can't share the money.