I think that the reason anyone believes in anything is because they've had experiences (be them events or thoughts) which, upon experiencing and upon recollection, feel undeniably 'real'.
You refer to a trip as being something like a movie played inside of our brains because of altered neurochemistry. But to examine and try to describe the neurological root of a given perception or feeling experienced during a 'psychedelic experience' i feel justly deems the examination and notation of the nature of 'sober perception'.
Are they not both subjective experiences? Is the 'movie' you speak of only playing when you trip? I feel it would be a strongly biased analogy without at least saying we're watching a dull movie while sober. :D Not to dis on your analogical representation, but really, Who EVER Sees Outside of One's Self? And the connotation of that question can be looked at mystically or scientifically. Really the difference is just the variation of the given chemicals effected....lol, not EVErYthing we see while tripping is fake...i swear some people when hearing a description of a trip will discredit all of it just because the person was 'altered' during it....my friend tried to tell me the sun didn't rise..because i said i saw it happen tripping
One of the main properties of psychedelics that i can note from my own experience is that they increase my energetic receptivity... hold on with me for a second, i'm not getting overly new agey...now, what this does is get me perceptually processing more information in a given amount of time as well as getting me to notice what is normally perceptually subtle.This property accounts for increased alertness and insane attention to details, as well as strong emotional reactions to experiences. The other main property and this is the Important part: increasing my energetic receptivity allows me to see the 'layers of my being'. No matter how hard i trip there's always the silent observer watching. when we wake, sleep, wander, we always see it happen at the core of ourself...higher self? spirit? or simply the guy in the control room of the brain...or maybe all of them

in front of the control room man is the mind, the emotions and then the externality (which is inconceivable without being digested by logic and baked to perfection by our perceptual facilities.)
sorry for the extended lengthiness, i am going to bring it all back together i promise. The 'avg joe experiece of reality', from what i've learned is like a shooken up jar of varying density liquids...ie oil, water, alcohol etc. When we keep running around, and performing action after action after action during our entire waking cycle, processing thought after thought after thought without rest for the mind, and experiencing emotion after emotion after emotion without ever taking time to make sense of them THEN we continue to shake the analogical jar of our being.
The resting of the jar happens when one is relaxed and at peace, and the liquids settle especially quickly when one meditating or becoming deeply centered through some other practice or sometimes through good discussion with a good friend.
So now the layers are visible....what do you see????? Well you, as the experiencer of existence, the control room guy, see yourself, the ego, the mind, the emotional being, the essence of your individual. And then WaaaaaaaYYY out there, you see what seems to be a world outside of yourself, something solid.
So WHat is in the layers...what is the Content of Our Selves? well....what have you made yourself to be?....look at your thoughts your ideas....feel the way you feel about the world. We always use our minds and our emotions, but we don't always have a clear view of the nooks and crannies of our minds and our emotions....and we can only very rarely can see the inter-relay of energy between these layers, ie the way your mind guides the emotions, the way emotions form your mind, the way your view of external reality is guided by your mind, the way your view of the outside world is rounded off (or overlooked because of) emotional fragility or rigidity.
When we look at our diagram of existential perception and consider that the mind is in front of the windshield the question comes up...what's on your mind?? or when we examine and dissect ourselves, what IN your mind...? The avg joe reality profile sees the mind as being our logic and the organizer of our information...but even scientifically, examination shows that there are many winding neuro-pathways and regions of activity in the brain at any given moment..we just 'normally' only see a surface level glimpse of our mind, and our mental selves. The function of this 'only seeing the surface' is very understandable though, when we take in too much information we often lose the ability to function.
To survive and especially to function in the social world, we have to keep our perceptions limited. just look at those hippies sitting around TRIPPIN OUT, they just go pet the leaves and dance around in the park..

...when we can see the societal constructs to their fullest we often spend all our time petitioning it or simply refusing it, giving further justification for crushing the ego's limitations (a possibly harsh cycle).
From my experience tripping is a combination of extreme energetic receptivity as well as extreme energy waves or energetic flanging. Kind of a yin and yang...you start to truly observe some subtle details while also having to now look through this dancing, flailing madman of a mind jacked up on psychedelic neuro-abstraction. Depending though, on the individual, the surrounding, and the particular flavor of neuroalteration present different perceptual experiences can manifest.
Many psychedelic experiences are rooted in delusional association...ie the table turned into a dog...considering table, firing to the dog, make it into a sandwich and call it NOW. Though much of the psychedelic experience for myself isn't focused on daydream imagery..it's more precise notice of symmetries and a strong tuning in to subtle perception. It's only when the level of energy being processed perceptually exceeds the ability of my perceptual facilities, or i am allowing myself to go all tangent artistic-like, that i really drift off into daydream experiences. I still have transcendental experiences and journeying...it's just not all inner-movies...it's extreme tuning in to the world around me.
For myself as well, this intense neuro-abstraction generally manifests not as delusional daydreams, but rather as artistic and/or analogical representations. Which, while being abstract sometimes, are DIRECTLY coordinatable into insight. Sometimes to the degree of personal revelations, but even as simply as two people looking at a pile of sand....the first walks away and says 'peh, sand...boring' and the second is too busy thinking of how we're all like little grains in the large pile of collective existence to notice the mundanity of the sand pile.
^^^All of that being said, i believe it is possible that there are energies out there...and even vibrational stimulus out there, which are not commonly received by our processing minds...and i think these are even less commonly perceived to anywhere near their fullest due to the hustle and bustle of the avg joe mindset. Just in terms of probability, there is so much energy out there and so much information that could be processed, it seems silly to assume that just because you have never experienced something doesn't mean it isn't an equally viable experience to be had. We have only ever been in our one place at our one time, and we've only experience these small fractions of what there is outside of us. Not only limited by our place in space-time, but also limited by our amount of perceptual receptivity.
Do you sit outside every day and just watch..? Do you take time out of your thoughts to listen..? Because if your actions that you choose to perform each day are not largely focused on sensing the world around you, then you're probably not running at 100% of your perceptual recognition. And even if you are perceiving 100% of the energetic stimulus around you (which is probably impossible even for a perceptual master lol) you are still only ever going to be experiencing a small fraction of the total energy in the world at any given time...and when you take into account the constant movement of energy, it starts to seem very probable that there are substantial experiences to be had that you have never seen anything like.
lol, scientists find new bugs sometimes...what if one of the ones unfound talks through mental waves...lol, a push, but a physical root to something that might be seen as, and rightfully is, entity contact. What if a subtle odor released from the processing of a given psychedelic draws these bugs near...what if you've been too busy sorting through your mind and emotions to notice what's been right in front of you..?
Or even better, what if there are many entities, always talking to us, but we can seldom decrypt their language into english....so it gets swept under the perceptual pile, going unnoticed by our conscious minds.
Surity lessens doubt, which increases surity...and true psychological delusional episodes are only truly delusion when there is no sense of doubt of the experiences...the schizophrenic who has doubt that maybe the govt isn't after him isn't completely delusional at that moment....
:D Food for Thought....Philosophy to Consider. IDEAS exploding out of my fucking head, and taking me a couple of hours to type. :D enjoy