Speaking as a theoretical physicist: we don't know that. What we do know is we have a better explanation for lightning within a conceptually simple framework (starting from a few simple principles) with predictive power, compared to an explanation that involves some mysterious old dude doing mysterious things with no evidence whatsoever. Could Zeus or Thor or whatever exist? Sure; there's no way to prove their non-existence. Do we need them to explain things? No.
It's similar here. We certainly don't need some elusive concept of "sentience" to explain chat bots. Not yet.
Speaking as a theoretical physicist: we don't know that. What we do know is we have a better explanation for lightning within a conceptually simple framework (starting from a few simple principles) with predictive power, compared to an explanation that involves some mysterious old dude doing mysterious things with no evidence whatsoever. Could Zeus or Thor or whatever exist? Sure; there's no way to prove their non-existence. Do we need them to explain things? No.
It's similar here. We certainly don't need some elusive concept of "sentience" to explain chat bots. Not yet.