I'm always surprised when otherwise fairly rational people are skeptical of the idea that we will ever create a conscious machine - in my view, this kind of viewpoint is unworkable without reference to some kind of immaterial "soul" or "spirit" which has arisen in biological life through some kind of supernatural means. As you said, -=SS=-, we are essentially just complex robots. The brain is the substrate of our consciousness and essentially a very slow, clumsily put together (such is the nature of all products of evolution) and unreliable biological computer. People have tried to estimate the storage and processing capacity of the brain before and although I can't remember the numbers off the top of my head compared to today's computerised hard drives and processors it really does not even compare... where the brain really shines, and where it demonstrates what evolution has been able to produce but we, so far, have not managed to replicate, is in the software of our consciousness, which demonstrates an incredible level of efficiency in processing and compression of memory data to understand and interpret problems that are still outside the scope of intelligent machines. If we accept that it is the software which gives rise to our consciousness then there is no reason this couldn't be replicated.
I'd like to propose a few thought experiments also - we already are at the point of being able to augment the brain's usual functions by implantation of electronics, such as the use of electrodes for Deep Brain Stimulation, and things such as wiring external devices to input systems that are not normally used for that purpose (ie, artificial "retina" cameras for the blind, which IIRC use the nerves usually reserved for auditory signals to allow them to "see" - over time the brain adapts to this unusual sensory input). There are also multiple companies working on methods to achieve more direct neural interfacing and read/write methods at the level of the individual neuron - on this basis I do not think it is too out there to presume that we will in the not too distant future be able to replicate the function of at least certain parts of the brain with technology.
A human being can survive a hemispherectomy (the removal of one hemisphere of the brain) which is a pretty rare procedure but sometimes performed in the case of severe epilepsy. This is interesting in itself as it raises the question of where in the brain our sense of self actually comes from... somewhere in the brainstem perhaps? Anyway, let's propose that at some point in the future someone is given an artificial hemisphere to replace the malfunctioning one that has been removed. What has happened to their "essence" or "soul"? Have they lost half of it? Or were they born without one? Let's say then, they go on to live a normal life, BUT they start to develop problems with the other hemisphere also, so this is replaced. Repeat the procedure for each individual element of the brain, going all the way down the brainstem, until their entire brain has been replaced with computational processing units. From their perspective, arguably, the change was gradual - their sense of continuity has not been interupted. But has their "soul" actually been removed because their brain is no longer biological in nature? If so, at what point did this happen? When their brain was less than 50% biological material by mass? I think that really any argument about the loss of a "soul" or "essence" in this kind of scenario is pretty arbitrary and hard to justify.
Let's try another thought experiment which I cannot say when or if it will be possible to do but does not seem outside the realm of technical possibility. We create a series of virtual reality scenarios to replicate the early conditions of life on Earth - these VR worlds are populated only with simulated, but simulated
biological bacteria (which are presumably not conscious). The simulations are sped up to billions of times normal speed so that we can watch the evolution of these primitive life forms into more complex forms. In some of the simulations, the VR beings that arise start to develop apparent intelligence and self-awareness, at which point the other simulations are paused or terminated and the seemingly conscious beings in the worlds where these evolved are uploaded into robot bodies. Is this apparent self-awareness just an illusion? Even though they came to be this way in a similar way to us, even if the substrate of their reality was at a more fundamental level, machine in nature rather than "natural" and biological like our own?
As far as I can see, the idea that true sentience or self-awareness can only exist in a biological being is a biocentric viewpoint and a form of the naturalistic fallacy where people just assume that things that are, arguably, "natural" have some inherent special quality that makes them better, "truer", "more real", or whatever. The only real arguments I can see in support of this viewpoint are either 1) sentience in a machine may be technically possible but it wil always be outside our ability to create this (which is perhaps arguable, but may be true), or 2) sentience in a machine is impossible because only biological life has souls (given to us by God, perhaps
, and something us mere mortals could never hope to do).
However I would be interested to hear any arguments to the contrary.
