Expert A is Elon Musk, polymath co-founder of PayPal, manufacturer of Tesla electric cars, creator of Space X, the first privately funded company to send a spacecraft into orbit, and much else besides.
''I think we should be very careful about artificial intelligence [AI],'' he told an audience at the Massachusetts Institute of Technology in October.
''If I were to guess what our biggest existential threat is, it's probably that.''
Mr Musk warned AI engineers to ''be very careful'' not to create robots that could rule the world.
Indeed, he suggested that there should be regulatory oversight ''at the national and international level'' over the work of AI developers, ''just to make sure that we don't do something very foolish''.
Expert B is Stephen Hawking, the world's most famous theoretical physicist and author of the best-selling unread book ever, A Short History of Time.
He has a brain the size of Denmark, and last Monday told the British Broadcasting Corporation that ''the development of full artificial intelligence could spell the end of the human race''.
Prof Hawking has a motor neurone disease that compels him to speak with the aid of an artificial speech generator.
The new version he is getting from Intel learns how Prof Hawking thinks, and suggests the words he might want to use next. It's an early form of AI, so naturally the interviewer asked him about the future of that technology.
A genuinely intelligent machine, Prof Hawking warned, ''would take off on its own, and redesign itself at an ever-increasing rate. Humans, who are limited by slow biological evolution, couldn't compete and would be superseded.''
So be very, very careful.
Mr Musk and Prof Hawking are almost 50 years behind popular culture in their fear of rogue AI turning against human beings (HAL in 2001: A Space Odyssey).
They are a full 30 years behind the concept of a super-computer that achieves consciousness and instantly launches a war of extermination against mankind (Skynet in the Terminator films).
Then there's The Matrix, Blade Runner and similar variations on the theme. It's taken a while for the respectable thinkers to catch up with all this paranoia, but they're there now.
So everybody take a tranquilliser, and let's look at this more calmly.
Full AI, with capacities comparable to the human brain or better, is at least two or three decades away, so we have time to think about how to handle this technology.
The risk that genuinely intelligent machines which don't need to be fed or paid will eventually take over practically all the remaining good jobs - doctors, pilots, accountants, etc - is real. Indeed, it may be inevitable.
But that would only be a catastrophe if we cannot revamp our culture to cope with a great deal more leisure, and restructure our economy to allocate wealth on a different basis than as a reward for work.
Such a society might well end up as a place in which intelligent machines had ''human'' rights before the law, but that's not what worries the sceptics.
Their fear is that machines, having achieved consciousness, will see human beings as a threat (because we can turn them off, at least at first), and that they will therefore seek to control or even eliminate us. That's the Skynet scenario, but it's not realistic.
The saving grace in the real scenario is that AI will not arrive all at once, with the flip of a switch.
It will be built gradually over decades, which gives us time to introduce a kind of moral sense into the basic programming, rather like the innate morality that most human beings are born with. (An embedded morality is an evolutionary advantage in a social species.)
Our moral sense doesn't guarantee that we will always behave well, but it certainly helps. And if we are in charge of the design, not just blind evolution, we might even do better. Something like Isaac Asimov's Three Laws of Robotics, which the Master laid down 72 years ago.
First Law: A robot may not injure a human being or, through inaction, allow a human being to come to harm.
Second Law: A robot must obey the orders given to it by human beings, except where such orders would conflict with the First Law.
Third Law: A robot must protect its own existence as long as such protection does not conflict with the First or Second Laws.
Not a bad start, although in the end there will inevitably be a great controversy among human beings as to whether self-conscious machines should be kept forever as slaves. The trick is to find a way of embedding this moral sense so deeply in the programming that it cannot be circumvented.
As Google's director of engineering, Ray Kurzweil, has observed, however, it may be hard to write an algorithmic moral code strong enough to constrain and contain super-smart software.
We probably have a few decades to work on it, but we are going to go down this road - the whole ethos of this civilisation demands it - so we had better figure out how to do that.
Gwynne Dyer is an indepedent London journalist.
