The Trolley Problem
The Trolley Problem is a logic problem which tests the morality of people. The propostion is that you see a runaway trolley car/tram careening towards 5 people. You can divert its cause by using a lever to direct the trolley car towards just one person on a seperate track. Doing so will mean intervening and definitely causing the death of one person. Objectively 1 life is worth less than 5 but the act of intervening makes the person imagining the problem to be responsible for someone's death rather than being witness to a tragic accident that kills 5 people.
The problem has seen a resurgence over the years with memes springing up on the internet as well as references in entertainment. The Netflix show 'The Good Place' explores several different versions and scenarios as it talks about philosophy.