## Thursday, October 27, 2022

### Probabilistic trolleys

Suppose a trolley is heading towards five people, and you can redirect it towards one. But the trolley needs to go up a hill before it can roll down it to hit the five people, and your best estimate of its probability of making it up the hill is 1/4. On the other hand, if you redirect it, it’s a straight path to the one person, who is certain to be killed. Do you redirect? Expected utilities:  − 1.25 lives for not redirecting and  − 1 lives for redirecting.

Or suppose you are driving a fire truck to a place where five people are about to die in a fire, and you know that you have a 1/4 chance of putting out the fire and saving them if you get there in time. Moreover, there is a person sleeping on the road in front of the only road to the fire, and if you stop to remove the person from the road, it will be too late for the five. Do you brake? Expected utilities:  − 5 lives for braking and  − 1 − 3.75 =  − 4.75 lives for continuing to the fire and running over the person on the road.

I think you shouldn’t redirect and you should brake. There is something morally obnoxious about certainly causing death for a highly uncertain benefit when the expected values are close. This complicates the proportionality condition in the Principle of Double Effect even more, and provides further evidence against expected-value utilitarianism.