Proximate Cause

Watch this video from the Palsgraf Case: https://www.google.com/#q=palsgraf%20lego%20site%3Ayoutube.com. 

The Dissent argues that the line between causation in fact and foreseeable causation is arbitrary. Remember that the railroad employee had no reason to know that the package contained explosives. So who does he owe a duty to? On the other hand, at what point should a person stop being responsible for all of the downstream consequences of his actions? For example, if you drop a lit match at the gas station and the explosion causes the elderly man on the next block to have a heart attack. Your act directly caused his injury, but should you be responsible? What about if you left your car in neutral at the top of the hill and it rolled down and killed a child. What if the child's mother, already depressed, begins taking opioids and robs her neighbor's house to get money to pay for her drugs? Are you responsible for that? At what point should the line be drawn? Discuss fully.