In a Q&A to celebrate Starfield's symbolic "gone gold" milestone (which has been reposted to the subreddit), lead quest designer Will Shen was asked if entirely non-lethal playthroughs will be possible in Bethesda's space RPG. They won't be, although Shen says that Bethesda did consider the possibility of supporting pacifist playthroughs early in development.
"We talked about this very early on during pre-production, whether or not we would fully support a 'non-lethal' playthrough," said Shen. "We realized that, for various reasons, that wasn't totally feasible."
Shen didn't go into the fine details of what makes pacifism infeasible in Starfield, but said that "there are some good non-lethal options" in the RPG, even if you're going to have to knock someone off eventually.
"Those [non-lethal options] can be used in certain situations, honestly a lot of situations, though I couldn't comfortably say you can complete the entire game without any killing whatsoever," Shen said. "The Settled Systems is mostly civilized, but it can be a dangerous place if you're going off the beaten path. And you're absolutely going off the beaten path!"
Starfield's "speech challenge" system is one of those murder-free conflict resolution options, and Shen said that it shows up in "most quests where important characters confront you."
It's not surprising that you're going to have to dispose of at least a few space assailants during Starfield's main quest. I doubt many have the patience to complete non-lethal runs in games that support them anyway, but it is always fun to know when the path is there.
The question got me wondering how a non-lethal Baldur's Gate 3 run would go, it being the RPG of the moment. You can certainly talk your way out of lots of BG3 conflicts, and NPCs will often go and kill each other if you don't stop them, which seems OK, since it isn't your doing. You can also "knock out" enemies with non-lethal melee attacks, so that when you are forced to fight, you don't have to kill. Knocked-out enemies are as good as dead, so it's a bit of a technicality, but sticking to KOs only would still be tough: No shoving people into chasms, no blowing them up with powder barrels, no finishing them off with spell attacks.
It's more fun to think about than do, for me: I've killed a lot of goblins in BG3 and I'll kill more, and I plan to blow up lots of spaceships in Starfield. With goblins in them, if there are space goblins. I'm happy to send apologies to their families, if that's an option.
