Thus we have no founded reason to doubt external reality.
The point is not based on doubting external reality. It's actually based on
not doubting it, then looking at our own abilities within real reality.
We have two possibilities. In this real reality, either it is possible for us to create a true consciousness through technology, or it is not. (There is a third hybrid option, but for argument's sake lets avoid that one for a moment).
If we assume that it is not possible to create a truly conscious AI, then there will be all sorts of philosophical issues arising. Chiefly, this would strongly argue that our own consciousness is not a product of material reality. Per your point about our senses, whilst our senses would give us the ability to perceive the universe, our reasoning faculty (cogito, ergo sum) -- or, consciousness -- would not be a by-product of a complex interaction of physical features and forces of this universe, but would be dependent on
something-else.
In other words, to posit that AI/simulated true-consciousness is impossible becomes proof of some sort of ordinal/subordinal relationship between our universe and another reality that ours exists within. This would be a proof of some sort of god. We will come back to this.
The other assertion, that it is possible for us to create a simulated true consciousness, will have other philosophical issues attached. First, it will prove that material reality is the only necessary condition for consciousness, which will, on the surface, suggest an atheistic reality. But there is an obvious point here -- if our consciousness arises not through some magical property delivered to us by some higher-order consciousness (a god, per the example above) but through the factual forces of the universe itself, then in order to create a simulated true consciousness there are two possible ways of doing it:
Option 1 - we create an AI in this world based on the same parameters that give us consciousness, which is, effectively, us. The only currently known forms of consciousness in the world are those which we see here on earth, so the AI we make will take shape and function in some way like life as we see it here. Another way of thinking of this would be a sort of accelerated evolution.
Option 2 - we create a simulation of a universe that is, for all intents and purposes, factual and "real." While it may only be a simulation to us, it has all the necessary conditions, per our own universe, to give rise to true consciousness
within it.
The consciousness that emerges within that simulation would perceive the universe it lives within as being the real reality. And to ensure there is no serious issue of information gain that destabilizes the simulated universe's balance of forces, it would seem likely that the consciousness within the simulated realty would only be aware of the reality it is within, and
not of the reality that its reality is within. That position of awareness would already be occupied by us.
If we assume that consciousness itself, per your sensory input argument, coupled with DesCartes' reasoning of the importance of reason in conjunction with the senses, is a form of verification of reality itself, then for the consciousness within the simulated universe
the simulation will be a real reality.
Consciousness, as a function of existence, is either a divine property or it is a physical property of the universe itself. If the latter, that means that universe gives itself reality by having the ability to perceive itself.
Therefore, this universe remains real
regardless of whether or not it is a simulation in a subordinal position to another universe.
So we aren't talking about a Matrix-style "you exist elsewhere but your mind is in a simulation" assertion. We are talking about the wholesale manufacture of real
realities.
Assuming the logic above is sound to even a small extent, then it is seems not only plausible but
likely that consciousnesses within a simulated real reality would have no need to know, or even
ability to know, that their real reality was a simulated reality in some other reality.
Given enough time and assuming "God" is not a prerequisite for consciousness, then the likeliest explanation of any universe is the existence of an ordinal universe that created it.
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Coming back to the matter of AI/true sim consciousness not being possible, the trouble here should be evident. If we can't create real consciousness, proving it not to be a property of this world but of another, then all we've actually done is prove the same thing -- that this universe/existence is subordinate to another and our consciousness is dependent on some other existing thing.
That would effectively demonstrate that this reality is, for all intents and purpose, a simulation.
No less real for being a simulation, but a simulation nonetheless.