It's not like seeing things that aren't there, it's like watching a movie, you know it's not real. It's kinda like two different visual channels, and perhaps hallucinations are what happens when people can no longer distinguish between the two...
You're missing the point. What if I told you I see an imaginary friend with me all day long. Everywhere I go, he is there doing his thing, making snide remarks and commentary that only I hear. I know he is not real, and I never get confused about that, but I see him nonetheless. You'd think that's weird, right?
I have the same opinion of people's purported "mind's eye" and visual imagination. Like, I'm able to recall things that I've seen, but they come back to me as grab-bag of feelings, abstract concepts, and an enumeration of qualities and characteristics. Not a reconstruction of a picture or anything like that, or a movie playing in my mind's eye or whatever.
This has never really been a handicap for me, except in art class which I was never any good at (Art teacher: "Just focus your mind on your subject while looking at the canvas, then just paint what you see. It's easy!" Me: "... wtf are you smoking?") Or when I went to pick up my fiancé from the airport after I first prolonged separation, and I got worried because I honestly couldn't remember what her face looked like.
But back to the analogy, it seems as if nearly everyone around me goes around life with an imaginary friend that only they can see, and I'm the only one who finds this weird. Like how can you even trust your senses if you're able to conjure up full sensual experiences in your imagination? I find this scary because it counteracts my own certainty: if my mind is seeing something or hearing something, IT'S REAL.
I figured since you'd never experienced it, I'd try to explain what it's like to you. For reasons I don't exactly understand, you keep trying to tell me what it's like instead! To compare it to a hallucination is a bad analogy, to compare it to an imaginary friend is an even worse one.
You have abstract thoughts, they just seem to lack a conscious visual component, but that's all the "mind's eye" is, thoughts. There's a distinct difference between your thinking and your physical experience.
>I'm able to recall things that I've seen, but they come back to me as grab-bag of feelings, abstract concepts, and an enumeration of qualities and characteristics.
Me too, and there's also "photographs" in there as well.
To me its almost like I have two separate canvases. One that my eyes render to and an 'offscreen' canvas my mind renders to. I can access both, but they don't overlap.
> Like how can you even trust your senses if you're able to conjure up full sensual experiences in your imagination?
Wow, this is fascinating, and it's incredibly hard to describe something you've just taken for granted!
When I'm writing this down, I can "hear" my own voice narrating what I'm writing, sometimes talking ahead as my typing catches up, sometimes the other way around. But I have no difficulty separating "real" sounds that have gone through my ears, from the sound of my mind's voice, if that makes sense. If I were to open my mouth and talk along with my mind's voice, it would become quiet, because there's now real sounds taking its place.
Visualizing things work sort of the same way, if someone says "think about a dog playing fetch!", I start seeing fragments/glimpses/moving images of my memories of dogs playing fetch, but it's more like having a movie screen in front of your eyes, I don't see the dog in the world as I see it, the mind's eye "sees" things on top of/in parallel to existing visual input. And staring at something that is visually boring, or closing your eyes, helps you see your mind's eye more clearly, since there's no overlap. The more visually interesting the real world is, the harder it is to clearly picture something in your mind. And just like with the mind's voice, you just know that what you're imagining isn't real.
So to answer your question: Actual hallucinations are what happens when you're unable to distinguish between the two, normally you have absolutely no problem doing so.