# An analysis of reality

This article by Dan Polansky analyzes the concept of reality. The concept seems very simple; the interesting thing about it is that it is not entirely straightforward to articulate.
A first sketch is this:
This sketch is deficient: optical fallacies and mirage lead to the mind forming a wrong impression/idea, but they are not a result of a dream. We may adjust the sketch to address these:
Here, we use the trick of "and similar" to cover cases we have not raised yet, without saying similar in what regards.
One may try another definition:
That is problematic since 1) the word "really" is left undefined, and 2) seeming/appearance are not the only forms of unreality.
Moving further, we may note reports of hallucinations in all sensory modalities. Thus, some people see (and hear, smell, etc.) things that are not there. But then, how do we know that not all sensory experience is hallucination?
This moves us to a further point, that of Descartes' demon and solipsism, the idea that the only thing existing is the mind and all its perceptions are just a result of a deception by a powerful demon (or Matrix).
There is also the simulation hypothesis: the world as we know it is a mere simulation, an analogue of a computer simulation. One may ask whether the simulacra are real. They can well be distinct from their reflections in the minds, and if so, the contrast between the extra-mental objects and their mental reflections is maintained, even if the extra-mental objects are mere patterns in the simulating substrate/hardware. One may then validly say that the simulacra are neither dreams, nor hallucinations nor mirage, and that there is something real about them, even if one may want to reserve the status of real for the simulating substrate/hardware.
Another point is that of causally isolated parallel universes. Are they real? They could be; we don't know. If so, it drives home one point about reality: in order for something to be real, there is no need for a mind to detect it or register it. But then, how do we know that what are arguably figments of imagination (e.g. J.R.R.Tolkien's world) are not real in some parallel universe? What makes us assert of such a world to be unreal despite lack of supporting positive evidence? To address such questions, we need to distinguish "X is real" vs. "X is known to be real". We see no reason to believe that imaginary/invented worlds are real and we therefore see their lack of reality as a solid working hypothesis.
Above, the working assumption is that there is the mind and the external world/reality, and that the mind can never be fully certain it knows the reality. Part of that assumption is e.g. that when a person is asleep, the brain and the world continue existing even while the sensory registering is largely turned off.
There is the phrase "objective reality". It implies a separate concept of "subjective reality". One can argue that all reality is objective reality, that is, that reality is by definition outside of the mind and anything subjective is by definition not reality. On the other hand, one can assert the reality of mental objects, including perceptions. Thus, "I had a dream" corresponds to reality if I in fact had a dream, and then, the dream--but not its objective content--is part of psychological reality. With this approach (allowing psychological reality), the result is a terminological confusion; the question of whether reality exists is then abolished since surely the mind exists and then at least psychological reality exists. On the other hand, the "I had a dream" argument in favor of admitting psychological reality has some force.
That's it about reality.