I’m going to take on the question of just what is reality anyway. This seems like it should be obvious on the surface, but when you start to examine it closely, that turns out not to be the case. Before I get started, let me point out that regardless of your theological or scientific stance, whether you believe in evolution or creationism, or what have you, the problem of defining just what reality is is somewhat problematic.
Let me start with the naïve definition of reality: reality is the stuff around me. This definition works for life in general because the environment in which I live is clearly important to my survival. In fact, it is probably the single most accurate definition of reality. The problem with it is how do we define “the stuff around me”, or even the term “me” itself. Clearly, if we cannot define those terms adequately, our definition of reality, while accurate, is not terribly useful to us.
Now let me examine the term “me”. It turns out that it is not necessary for me to be self aware or even able to think (the two are orthogonal concepts) in order to have a reality so let us leave aside the debate about what makes a person and all that complication. In fact, I need not even be able to perceive the things around me for them to exist. Instead, let us consider the term “me” in the definition to simply be the object or creature whose reality we wish to define. Then we can consider the “stuff around me” phrase to refer to every aspect of the environment in which I find myself. For instance, if a hypothetical being called Fred builds a robot and puts it in a box that is one mile in each of three dimensions and fills that box with a mount of dirt and an atmosphere, we can say that reality for that robot is the contents of the box and the inner surface of the box itself. We can also argue that Fred’s reality is also part of the robot’s reality, and then anything Fred’s reality is contained in. Pretty soon, it’s turtles all the way down. In order for this regression process to stop, there has to be on objective reality that is not contained within any other reality. And here, we run into the problem with defining reality objectively. While there may, in fact, be such an objective reality, we have no way of observing it because we are, ourselves, part of a reality.
So if we cannot divine the existence of an objective reality, the naïve definition of reality cannot be useful when extended to its logical extremes. Instead, let us consider the notion of subjective reality. That is the idea that my reality depends on how I perceive it. Regardless of your beliefs, you will probably agree that we all have several senses including sight, hearing, and touch. You may believe in the psi arts or you may not, or you may believe in telepathy, or not. But you will agree that we all have senses which we use to perceive the world. The precise nature of these senses affects what we perceive. For instance, if our eyes are set up to observe a particular set of electromagnetic wavelengths by focusing them on a mostly flat surface (as they are generally accepted to do), our perception of electromagnetic radiation is limited to those frequencies and to a two dimensional projection of the visible radiation from the direction the eye is pointed. In our case, we do not see radio waves so radio waves are not part of our reality. (Yes, I know. I will get to that in a moment.) A similar thing can be said for hearing, or touch, or telepathy, or whatever other sense you might imagine.
In other words, my subjective reality is everything I can perceive with my senses. Again, self awareness and thought are not required for this. An inanimate object orbiting a star will “feel” the radiation of the star, for instance, and that would be part of its subjective reality. However, something which happens so far away that the light from that event has not yet reached the object is not part of its subjective reality (thought it might be considered part of the objects objective reality).
Now let’s consider the nature of “me” again. We must assume that there is such a being as “me” for this discussion. I will assume that “me” is rooted in my brain, but the argument is the essentially same if you assume “me” is rooted in some amorphous soul or some other thing. So the collection of squishy stuff in my skull is what allows me to think, be aware of my existence, and so on. But how do I know that? That collection of squishy stuff cannot perceive directly its own existence. It must rely on the sensor package that is part of its support system (my body). Even then, I cannot, using my own senses, directly perceive my own brain, and even if I could, I would not be able to directly perceive how it does what it does, so I still cannot perceive myself directly. I can perceive my body, to various degrees, however, such as looking at my hands as I type this, or feeling the ache in my knees or the fact that I am neither cold nor hot. Using my senses, I can see the display screen and the various clutter on my work table. I can see the walls of my office, and if I relocate, I can look out at my back yard.
What I have just described is what most people would call “the stuff around me”. In other words, our original naïve definition of reality can just as easily be interpreted as a subjective definition as it can an objective one. So I can rephrase it as “my reality is the sum of everything I perceive through my senses”. But that is not yet complete for it fails to take into account my capacity to remember, to learn, to believe, and to imagine.
This is where most disagreements about the nature of reality really begin. For instance, I believe, for whatever reason, that my consciousness vests in the squishy stuff that exists inside my skull while someone else might imagine that their consciousness exists independently of the squishy stuff in their skull. I believe what I do partly because I have been told that is the case by people who I perceive to be trustworthy and partly based on some evidence I have collected on my own. The other person mentioned believes as he does for similar reasons. The two of us may even disagree on the meaning of specific evidence or even what constitutes evidence, or it may even be a simple matter of faith (belief without necessarily having evidence or reason).
Remember my comment that radio waves are not part of my reality because I cannot perceive them? Once you bring memory, learning, belief, and imagination into the mix, radio waves easily become part of my reality. This is because I have chosen to believe they exist for much the same reason I believe in the squishy stuff in my skull. I have seen evidence that something behaving a great deal like how radio waves are supposed to behave seems to exist, allowing such wonders as cellular telephones and AM talk radio. In other words, I have indirectly perceived the existence of radio waves and I remember having done so. This has allowed me to believe in their existence. Thus, my reality consists also of those things I can indirectly perceive.
Finally, I can imagine things. Essentially, this is pretending something is the case for whatever reason (entertainment, discovery, etc.). For instance, I imagine my words to be worthy of your time to read, and thus I take my time to write them. I can equally imagine that a Time Lord calling himself The Doctor wanders around time and space in a dimensionally transcendental blue box. These things, too, become part of my reality, though I am capable of differentiating between those things that are “real” and those things that are imaginary. Real things are those which other apparent inhabitants of my reality agree is real. Thus, the Time Lord is imaginary though the collection of stories in which he features are real.
Now to the point of talking about imagination. Suppose I am incapable of interpreting the Time Lord stories as fiction? Suppose I am incapable of separating reality from imagination? What, then, does that mean of my reality? Why, it means that my reality would include also those things that other apparent inhabitants of said reality deem to be fiction. This is often referred to as a delusions. Thus, my reality is also formed from my delusions.
It is useful here to define two terms. Internal reality is that component of subjective reality that is internal to me, that does not depend on my senses. This is my memories, my imagination, my beliefs. External reality everything I perceive through my senses. There is some overlap here, in the case where I believe I perceived something with my senses but it turns out to be a delusion, a belief if you will. There is also a feedback between the two for what I know and remember affects how external reality is perceived and external reality will tend to affect internal reality as memories form or I learn new things from it.
Finally, here is the mind blower. What if everything I perceive to be my reality is all a fiction? What if I am that robot in a large box? Indeed, what if I am that robot’s brain and it is only being fed the idea that it is in a large box? What if all of my external reality is being synthesized by Fred and fed into my brain directly, with no sensory apparatus at all? What if everything I feel, see, touch, smell, hear, and taste is all simulated by Fred? Does that change my subjective reality? Not really. After all, I can only perceive the world around me through my senses and if they are being manipulated by Fred, I have no way of knowing that.
Let me sum things up. There must certainly be an objective reality somewhere in which I exist. It’s possible that nobody else does exist (though you will no doubt turn that around and cast yourself as “I”). However, because I can only know my subjective reality, there is no possible way I can know what that objective reality truly looks like. It may even be the external reality I perceive with my senses! However, the precise nature of my external reality cannot be known by me because I can only perceive it through my own senses and those senses could just as easily be manipulated as accurate.
The real question that should be answered is this: Does it matter if I am just a brain in a box experiencing a world synthesized by Fred? My contention is that it does not matter to me for I have no way of knowing that is happening! The concept merely serves as an interesting mental exercise. (If you think about it, you will see that the same argument can apply to the idea that the Earth is only 6000 years old; supposing that to be true, it is obvious that when it was created, it was designed to look over 4 billion years old and we have not yet found an error in that design. It can also be applied to a great many other philosophical or theological debates. In other words, it’s turtles all the way down.)
My overall point of this ramble is that whether reality is real, or even what reality actually is, is fundamentally unknowable by us. Thus, any attempt to argue from authority based on something being “real” is simply doomed to be logically unsound. One must always assume some sort of reality (axiomatic system) in which to ground ones logic, whether that be the particular consensus reality of science or that of a particular religion, or even that of an imaginary world, does not matter. What matters is that all participants in a logical debate must agree on the same basic axioms of reality. Without that agreement, no true debate is possible.