The Search for Extra Terrestrial Life (SETI) names the globally distributed projects, people and institutions that search the cosmos for signs of intelligent life. SETI's methods mostly entail scanning for the emission of electromagnetic radiation, an exhaust that is assumed to emanate from civilizations with advanced technologies.
Like the quest to build intelligent machines, the search for intelligent aliens makes assumptions about what intelligence is, and what aliens are. SETI assumes that alien life would be intelligent if it matches humans' science-fictional expectations for intelligence. More or less: animalian creatures with communication devices and spaceships and the like.
Critics of SETI sometimes invoke what are called "uniformitarian" objections. Uniformitarianism names the assumption that the same conditions and laws apply everywhere, throughout time and space. SETI is uniformitarian in its assumption that all alien intelligence would be the same, namely, like human intelligence (but smarter, of course). But it's just as compelling to think otherwise. The philosopher Nicholas Rescher, for example, has observed that if there is intelligence in the universe, it's possible we humans wouldn't even be able to identify it as intelligence. Truly alien intelligence would differ from us not only in its cosmic location, but in its very nature as well. As Doris and David Jonas put it some forty years ago, different sensory capacities produce different "slits" for perceiving, explaining, and interacting with reality.
This means that alienness is not just "out there" but all around us. You might find your cat to be intelligent in a certain way, or your smartphone, or your car, or a hypothetical future robot, or, given the right perspective, even your houseplant or your toaster.
The dream of thinking machines is really no different than the dream of intelligent aliens. It just replaces the biological, cosmic entropy-fashioned alien of afar with the mechanico-electronic, human-fashioned machine in our midst. And if SETI and its kindred make a uniformitarian mistake in the cosmos, efforts to theorize and create artificial intelligence and thinking machines make the same one here on Earth.
Perhaps the best evidence for thinking machines' reliance on the particular mode of "intelligence" that humans experience can be found in our fictional doomsday worst-case scenarios for AI. The fear of a robot or computer apocalypse of the Terminator or Berserker or Matrix varieties depends on machine intelligence besting humans to the point that it realizes the best option is to destroy and replace it (or, in the Kurzweilian singularity version of AI fantasy, humans willingly submit to their computer overlords in order to achieve immortality). Closer to home than to doomsday, our fear of machine intelligence also expresses itself in a concern over the role of human thought and labor in an economy run more and more by mechanical and electronic machines.
This is one vision of and for thinking machines, but it need not be the only one. Thinking about thinking machines turns out to be so narrow and anthropocentric, it's surprising that we haven't given up on it out of boredom rather than on contra-uniformitarian grounds. Rather than asking if machines can think, or what we need to do to cause them to think, or how we would know if they were thinking, what if instead we just assumed that all "machines" did something akin to "thinking," and then attempted to characterize what thinking might mean?
In philosophy, there are already directions toward such an approach. Contrary to the emergentist position that most AI advocates hold—that mind emerges from specific material conditions, whether in biological or computational entities—panpsychists take the position that "minds" are everywhere, in some sense. Panpsychism bears some relationship to certain Buddhist doctrines, which encourage the awareness of the animism in nature. But panpsychism risks the same erroneous uniformitarianism as SETI or AI, namely that a mind akin to that of a human (or at least an animal) is the model for all other minds. A more promising philosophical position is that of panexperientialism, the position that everything has something like experience, even if the experience in question might be very different from that of a human being.
When we think about machines that think, we usually think of a particular sort of machine, and a particular sort of thinking—electronic, and (super)human, respectively. But what if, instead, we allowed for the possibility that we've been missing out on all the "thinking" being done by all the other kinds of machines that surround us. Computers and robots, for sure, but also toasters and garage doors and automobiles. This may seem like a ludicrous waste of time on first blush, but it doesn't take long enough to prove useful. If the purpose of thinking about thinking machines like AIs and robots and computers is, in part, to struggle with the question of what living with them as neighbors and companions and even citizens might look like, then we ought to start by taking more seriously all the machines that already surround us, that could be said already to take on those roles, and which we nevertheless ignore.