I suspect people can "feel so sure" because they can feel, and see no evidence that computers can.
But that's a dangerous edge to walk regardless. Humans feel, computers don't - most would agree. Humans feel, animals don't - many would agree, many would not, many would draw a finer line between e.g. mammals and others. Humans feel, inferior-race-X does not (frequently argued about slaves) - many would disagree, but obviously many do think this is true.
For myself: I've seen nowhere near conclusive proof either way, and continually-increasing evidence in favor of human == machine.
But that's a dangerous edge to walk regardless. Humans feel, computers don't - most would agree. Humans feel, animals don't - many would agree, many would not, many would draw a finer line between e.g. mammals and others. Humans feel, inferior-race-X does not (frequently argued about slaves) - many would disagree, but obviously many do think this is true.
For myself: I've seen nowhere near conclusive proof either way, and continually-increasing evidence in favor of human == machine.