There is a train that, much to your horror, is about to run over your grown up son, who has been tied to its track. It just so happens that you have just enough time to flip a switch that will send the train down a different track, saving your son. However, tied to the other track, is your granddaughter, the daughter of the very son in danger of being run over. Your son is begging and pleading with you not to flip the switch, not to kill his daughter. What would you do?