Toby Ord’s definition of an existential catastrophe is “anything that destroys humanity’s longterm potential.” The worry is that misaligned AGI which vastly exceeds humanity’s power would be basically in control of what happens with humans, just as humans are, currently, basically in control of what happens with chimpanzees. It doesn’t need to kill all of us in order for this to be a very, very bad outcome.
E.g. the enslavement by the steel-loving AGI you describe sounds like an existential catastrophe, if that AGI is sufficiently superhuman. You describe a “large portion of humanity” enslaved in this scenario, implying a small portion remain free — but I don’t think this would happen. Humans with meaningful freedom are a threat to the steel-lover’s goals (e.g. they could build a rival AGI) so it would be instrumentally important to remove that freedom.
Reply by reallyeli on the EA Forum: