By one definition of the word "think"—to gather, process and act on information—planet Earth has been overrun by silicon-based thinking machines. From thermostats to telephones, the devices that bring convenience and pleasure to our daily lives have become imbued with such increasingly impressive forms of intelligence that we routinely refer to them, with no hint of irony, as smart. Our planes, trains and now our automobiles too are becoming largely autonomous, and are surely not far from jettisoning their most common sources of dysfunction, delay and disaster: human operators.
Moreover the skills of these machines are developing apace, driven by access to ever-larger quantities of data and computing power together with rapidly improving (if not always well understood) algorithms. After decades of over-promising and under-delivering, technologists suddenly find their creations capable of superhuman levels of performance in such previously intractable areas as voice, handwriting and image recognition, not to mention general knowledge quizzes. Such has been the strange stop-go pattern of progress that someone transported here from five years ago might well be more astonished at the state of the art in 2015 than another time traveller from fifty years or more in the past.
But if the artificial intelligence industry is no longer a joke, has it morphed into something far worse: a bad horror movie. Machines can now know much more than any of us, and can perform better at many tasks without so much as pausing for breath, so aren't they destined to turn the tables and become our masters? Worse still, might we enter a cycle in which our most impressive creations beget ever-smarter machines that are utterly beyond our understanding and control?
Perhaps, and it's worth considering such risks, but right now these seem like distant problems. Machine intelligence, while impressive in certain areas, is still narrow and inflexible. The most remarkable aspect of biological intelligence isn't its raw power but rather its stunning versatility, from abstract flights of fancy to extreme physical prowess—Dvořák to Djokovic.
For this reason humans and machines will continue to complement more than compete with one another, and most complex tasks—navigating the physical world, treating an illness, fighting an enemy on the battlefield—will be best carried out by carbon and silicon working in concert. Humans themselves by far pose the biggest danger to humanity. To be a real threat machines would have to become more like us, and right now almost no one is trying to build such a thing: it's much simpler and more fun to make more humans instead.
Yet if we're truly considering the long term then there is indeed a strong imperative to make machines more like us in one crucial—and so far absent—respect. For by another definition of the word these machines do not "think" at all because none of them are sentient. To be more accurate, we have no way of knowing, or even reliably guessing, whether any silicon-based intelligence might be conscious, though most of us assume they are not. There would be three reasons for welcoming the creation of a convincingly conscious artificial intelligence. First, it would be a sign that at last we have a generally accepted theory of what it takes to produce subjective experience. Second, the act of a conscious being deliberately and knowingly (dare I say consciously?) constructing another form of consciousness would surely rank alongside the most significant milestones in history.
Thirdly, a universe without a sentient intelligence to observe it is ultimately meaningless. We do not know if other beings are out there, but can be sure that sooner or later we will be gone. A conscious artificial intelligence could survive our inevitable demise and even the eventual disappearance of all life on Earth as the Sun swells into a red giant. The job of such a machine would be not being merely to think but much more importantly to keep alive the flickering flame of consciousness, to bear witness to the Universe and to feel its wonder.