When I am lecturing and I discuss possible future interfaces in which people use glasses or contact lenses or perhaps eye implants to see virtualized versions of reality, I often get variants on the following question: Isn’t this all taking us away from reality?
My standard answer is that we already live in virtual reality. Every communication technology ever invented is a form of virtual reality. It’s just that after a while we become used to any given artificial mode of communication, and then we relabel it as reality.
But I think there is a more specific principle at work here: “Natural” is not really about the absence of technological intervention, or even about how much or how little technology is involved.
Rather, there is only sensible question to ask about how “natural” a technology is: How well does it fit our current state of human biological evolution?
Humans have evolved over millions of years toward a particular kind of brain and a particular kind of body. This biological evolution, which occurs over extremely long periods of time, has essentially been at a fixed point throughout the entire history of human civilization (an extremely tiny span of time in evolutionary terms).
So we are pretty much stuck with these brains and these bodies. Of course we can perform technological interventions to make them operate differently. For example, written language is a technology that allows humans to transfer knowledge to other humans who will not even be born until centuries later. This remarkable technology works only because it is consistent with the capabilities of our human biological brains — which are essentially the same brains that the Cro Magnon possessed 35,000 years ago.
Similarly, automobiles and musical instruments are designed to be operated by human brains and bodies. We don’t need to change our biological self to play the instrument or to drive the car (nor could we). Rather, we design the car or the piano to work with our existing brains and bodies.
It is not our brains or bodies themselves that evolve over time, but rather the technologies that we create to work with them. So I would argue that a “natural” interface is one that works well with this current biological fixed point in the evolution of our species, and therefore can be gracefully and widely adapted by our species.
It makes no difference how “weird” a technology might have seemed in earlier times. At some point in the past, before their invention, a car or a telephone might have seemed completely alien to the humans of that earlier era.
And so, if it turns out that humans some day end up using computerized lens implants, and that such a technology meshes well with our biological nature, then that will be a natural technology. Whether that technology would have been seen as natural by a previous generation is ultimately irrelevant.