You are standing on a bridge overlooking a track where five dogs are sitting. Suddenly, you see a trolley coming down the track. The dogs are not paying attention, and if the trolley hits them, they will surely all die. You start to panic, but then you see that next to you is a very fat dog. You could push the dog off the bridge, killing him and stopping the trolley. Should you do it?
You are a private veterinarian who takes care of stray dogs. You currently have five dogs who all need a different organ to survive, and you have no doggy organ donors. You are about to give up hope when a healthy dog walks in for a doggy check-up. You could kill him, harvest his organs and give them to the other five dogs. Should you do it?