A penny for your thoughts? You may not choose to answer. But the point is that, as a conscious agent, you surely can. That's what it means to have introspective access. You know—and can tell us—what's on stage in the theatre of your mind. Then how about machines? A bitcoin for the thinking machine's thoughts? But no one has yet designed a machine to have this kind of access. Wittgenstein remarked that, if a lion could speak, we would not understand him. If a machine could speak, it would not have anything to say. "What do you think about machines that think". Simple. I don't think that—as yet—there are any such machines.
Of course this may soon change. Far back in human history, natural selection discovered that, given the particular problems humans faced, there were practical advantages to having a brain capable of introspection. Likewise machine programmers may well discover that, when and if machines face similar problems, the software trick that works for humans will work for them as well. But what are these problems, and why is the theatre of consciousness the answer?
The theatre lets you in on a secret. It lets you see how your own mind works. Observing, for example, how beliefs and desires generate wishes that lead to actions, you begin to gain insight into why you think and act the way you do. So you can explain yourself to yourself, and explain yourself to other people too. But, equally important, it means you have a model for explaining other people to yourself. Introspective consciousness has laid the ground for what psychologists call "Theory of Mind."
With humans, for whom social intelligence is the key to biological survival, the advantages have been huge. With machines, for whom success in social life has not yet become an issue, there has been little if any reason to go that way. However there's no question the time is coming when machines will indeed need to understand other machines' psychology, so as to be able to work alongside them. What's more, if they are to collaborate effectively with humans, they will need to understand human psychology too. I guess that's when their designers—or maybe the machines themselves—will follow Nature's lead and install a machine version of the inner eye.
Is there a danger that, once this stage is reached these newly insightful machines will come to understand humans only too well? Psychopaths are sometimes credited with having not too little but too great an understanding of human psychology. Is this something we should fear with machines?
I don't think so. This situation is actually not a new one. For thousands of years humans have been selecting and programming a particular species of biological machine to act as servants, companions and helpmeets to ourselves. I'm talking of the domestic dog. The remarkable result has been that modern dogs have in fact acquired an exceptional and considerable ability to mind-read—both the minds of other dogs and humans—superior to that of any animal other than humans themselves. This has evidently evolved as a mutually beneficial relationship, not a competition, even if it's one in which we have retained the upper hand. If and when it gets to the point where machines are as good at reading human minds as dogs now are, we shall of course have to watch out in case they get too dominant and manipulative, perhaps even too playful—just as we already have to do with man's best friend. But I see no reason to doubt we'll remain in control.
There is a painting by Goya of a terrible Colossus who strides across the landscape, while the human population flees in terror. Colossus was the name of one of Turing's first computing machines. Do we have to imagine an existential threat to humanity coming from that computer's descendants? No, I look on the bright side. With luck, or rather by arrangement, the Colossus will remain a Big Friendly Giant.