I think thinking about machines that think is the most interesting thing to think about. Why? Because the possible implications of this phenomenon are profound. Cosmic even.
First I claim that "thinking machines" have already been with us for a long time. There are two ways to understand this, depending on which word you start with. Let's start with "machines" first, and by that, these days we really mean computers.
Computers started out, well, pretty mechanical. But they keep getting more and more subtle. Even the computers of the 80s could perform some remarkable feats with expert systems and databases. Today we have passed the point where a person can explain in detail how voice recognition and natural language allow their phone to answer a question spoken by a child. "Magical" is hardly a hyperbole. But is this really "thinking"? Not yet but it's a good start, and the trend is accelerating. True, the goal still seems so far away. Instead of considering our climb, step by step, look up and consider what lies at the top of the mountain. Is there anything that can halt our progress?
Certainly the future of chip technology is in doubt. Moore's Law has been very good to us, and it has dodged a few bullets, but it is ending. Historically, new technologies have appeared just in time to keep the exponential growth of computation on schedule, but this is no given. Perhaps the next leap is incredibly difficult and will take 50 years. Or perhaps it will never happen, but we can always add more chips in parallel. The schedule is an interesting question. But for me, it pales in comparison to pondering the destination.
Now let's start with the word "think." The other way that thinking machines have been around for a long time is ourselves. Biological brains have been thinking for millions of years. And perhaps it is controversial but I claim a brain is a machine, in a limited way: brains follow the laws of physics, which are a mechanical set of equations. In principle, a good physics simulator could, very slowly, simulate a brain and its environment. Surely this virtual brain would be a machine that thinks.
The remaining question is how much physics is required to make the simulation work? Would classical physics, electricity and chemistry do? Would quantum logic (or beyond) be required? The consensus is strongly in favor of the idea that classical physics suffices (The Emperor's New Mind has been rejected). Hence I think of my brain and body as a giant machine made up of an octillion molecules: many, many tiny magnetic tinkertoys whose behavior is very well understood, and can be simulated. In fact there are good reasons to believe a statistical approximation of physics can provide the same results while skipping the details. But again, this only affects the schedule, not the destination. The important question is, how does thinking and consciousness emerge from this complex machine? Is there some construction, some bridge, from the digital and virtual to the analog, organic, and real?
These threads meet with the merger of human and computer substrates. Smart phones are rapidly becoming indispensable parts of ourselves. The establishment has always questioned the arrival of new media, but adoption of these extensions of ourselves continues apace. A lot of ink has been spilled over the coming conflict between human and computer, be it economic doom with jobs lost to automation, or military dystopia teaming with drones. Instead, I see a symbiosis developing. And historically when a new stage of evolution appeared, like eukaryotic cells, or multicellular organisms, or brains, the old system stayed on and the new system was built to work with it, not in place of it.
This is cause for great optimism. If digital computers are an alternative substrate for thinking and consciousness, and digital technology is growing exponentially, then we face an explosion of thinking and awareness. This is a wave we can ride, but doing so requires us to accept the machine has part of ourselves, to dispense with pride and recognize our shared essence. Essentially we must meet change with love instead of fear. I believe we can do it.