Should we forcibly harvest a man’s organs to save five people? Should we plug the whole of the humanity into a machine that could ensure the maximal amount of aggregate pleasure if we could? Are we obligated to save a child drowning in a pond? These are all famous thought experiments that philosophers have posited over the past century to sway us over to their way of thinking and appeal to our most basic intuitions. But this practice, argues Edouard Machery, is dangerously flawed.

You’ve probably heard of the famous Trolley case. Here is one version: suppose a runaway trolley is about to hit five workers who, by accident, happen to be working on the track. The only way to prevent their death is by pushing a switch that will redirect the trolley onto another track. Unfortunately, there is another worker on this sidetrack who will be killed if the switch is pushed. The question: Is it permissible to push the switch, saving five people but killing one?