I think he refers to an old philosophical question.
The classic example is 'you're conducting a train. You come around a bend, and there's a track split. One track A is, say, a person. On track B is, say, two people. You don't have time to brake. All you can do is pick which track you take. Which one do you take?
What if Track B has five people? One child? A world-class doctor who saves lives? A scumbag criminal? Your wife?
So, say you're in a self-driving car. The car wants to make a left turn across traffic at a four-way intersection. So it advances into the intersection, stops to wait for a break in oncoming traffic, and waits.
Sensors notice a semi coming up behind you, and not stopping. In front of you is an old person crossing the road. To your right is a kid on a bicycle. To your left is a stead stream of through traffic. Where do you go?