Also a factor in emergencies is time. So that if you don’t have enough time to weigh the evidence and instead make a snap decision, you really aren’t responsible if that decision turns out to be in conflict with your values.
You know, I’m amazed every time I face an emergency, be it minor or major, how much thinking my subconscious can accomplish in such a short time. True, you lack the time to evaluate, or even observe, all factors. Therefore your desicions are more likely to be wrong or even in conflict with your values.
As for what to do in an emergency, that’s what foresight is for. Every so often, I consider my surroundings and think “What would I do in case of fire, or an earthquake, or a flood?” I do this particularly when traveling, especially in airplanes and hotels. Because once the emergency hits, you won’t have time to figure out what to do in a strange place.
In the specific example, rescuing a stranger, it depends on many factors -the most important being the risk to yourself. If the risk is negligible, then you should dive after the drowning child. How big a risk you’re willing to take and for whom, though, is a personal decision.
Suppose you can’t swim and a child is drowning in a river. You’re as likely to drown as to provide minimal help. the rational thing to do would be to yell for help, or to try to help from outside (throwing ropes, branches, anything that floats, etc). Diving in would be irrational, because you’d be sacrificing your life for no purpose.
And those are the easy scenarios. Anything else is much more morally complex.