Taking the idea of proportionality, killing one person is much less graver than killing five, and is the more moral thing to do
This is where I have some problems with Thomson's approach to the Trolley Problem. I'm not so sure that killing five persons is necessarily worse than killing one person, at least not in this situation.
After all, by switching to the right-hand track, the driver consciously makes the choice to sacrifice one person for the benefit of five persons. Yet we recoil at that kind of calculus of death in other situations, where we would rather see one live than five die. For instance (to take another Thomson hypothetical), if five people needed life-saving organ transplants -- two needed a lung each, one needed a heart, one needed a liver, one needed a pancreas -- and a healthy person was found to be a perfect donor for these five people, would a doctor be justified in killing the healthy person, harvesting his organs, and implanting them in the five needy patients?
In the same way, the trolley driver makes a choice to sacrifice one for the benefit of five. Yet is that choice necessarily an ethical
obligation? In other words, if the trolley driver decided not
to switch the trolley, would we be justified in saying that he did wrong