system
Given the following post, respond as if you're commenting on Reddit:
human
From a utilitarian perspective, how far do the consequences of an action extend?

If one person was killed, how far would the negative consequences be calculated? You could factor in the utils lost from their friends, and people immediately close to them, people who find out about the death, but how far could it go from there? Would you factor in the happiness the person would’ve felt during their lifetime? The happiness of the descendants they could have created? Is there really a limit to how many factors are involved in calculating  the utility of a single action?
gpt
Right - *every* consequence matters. To give a full accounting, you would need to consider the entire history of the universe causally downstream of the event you are evaluating.

Of course, it's impossible for anyone to know all of that (not just practically impossible, but likely physically impossible). So it's impossible to know for sure what the value of an act is.

Utilitarians don't recommend doing the calculation itself to figure out what to do - the calculation is what a hypothetical spectator with the perspective of the universe would do to figure out which acts really were good or bad. They just tell us to try to do the things that will come out well on this calculation. We likely won't always succeed, but we can develop some rules of thumb that will help us guess decently well. In general, killing someone is usually going to come out negative, as is injuring someone, and usually killing more people will come out worse than killing fewer.