If reality is what we perceive and experience... ...does that make it 'perception input'? .. or output?
Just whatever that extrospective environment's own unfolding "story" says is going on, a reality which features the brain / body as residents of itself rather than their being or having meta-phenomenal counterparts. That is, the empirical body isn't "outputting" the world which it is featured as a denizen of. That would be like Bugs Bunny being responsible for producing the cartoon he's surrounded by. Or Captain Nemo uselessly speculating that there's some other reality outside his novel where submarines turned out to be built or powered differently than the Nautilus.
Jules Verne didn't break down a fourth wall
for the sake of characters in 20,000 Leagues
, but that surely can't be said for all Warner Bros cartoons. Yet even with any instances of the latter, it's a kind of pseudo- breaking down of the 4th wall; of addressing a "hidden audience" or vice versa, that's likewise part of the story rather than exposing legit transcendent "viewers" [footnote at bottom].
In the context of commonsense, our intersubjective reality's internal story asserts that the external world is already much the way in which humans perceive and understand it, prior to the explanation of information about it being inputted to the body. A passive perception, no more altering or creating public happenings than an unreasoning video camera and microphone does. Scientific adjustments may break down a "fourth wall" and expose / hypothesize all manner of weird and disturbing items [yielding indirect perception]; but this again can be regarded as a pseudo-breaking down of a 4th wall, a faux transcencence, like in the cartoons mentioned above (still part of the internal, unfolding story rather than genuinely escaping it).
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[footnote] Purely figurative; the transcendent in general would not have to consist of personhood or possess observational powers, or even exist (for the radical positivist / empiricist). Apart from the necessity demanded by morality and social prescriptions for other minds being the case; Hugh and Sue and Drew and the rest should be assumed to be more than their superficial, outer appearances. Even measuring their organs and cells and atoms is still an outer perspective, what it's like to examine the "other" rather than be it. Though in the case of humans we "know" from our own internal-ness what being a person is like.
A rock or chair or moon is taken to be non-conscious and nothing at all in itself, if extracted from the interdependency of what they are in the public world and our descriptive / technical understandings of them. But this does not seem quite right; just as Kant left something remaining to signify existence on the noumenal side. He also left something unknowable as a validating experience lingering on the noumenal side of humans, as well. Experience or 'what it's like' -- the merger of concepts and appearances, was certainly not the "thing-in-itself"-ness of ourselves in his philosophy, as I might seem to be suggesting above. Panpsychists or panexperientialists wouldn't agree, of course.
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Reports to the brain about the status of sensitive body tissues that evolution found it handy to turn into a reality simulation. Not necessarily referring to dreams, as Nietzsche did below.
Now, the dream is a seeking and presenting of reasons for these excitations of feeling, of the supposed reasons, that is to say. Thus, for example, whoever has his feet bound with two threads will probably dream that a pair of serpents are coiled about his feet. This is at first a hypothesis, then a belief with an accompanying imaginative picture and the argument: "these snakes must be the causa of those sensations which I, the sleeper, now have." So reasons the mind of the sleeper. The conditions precedent, as thus conjectured, become, owing to the excitation of the fancy, present realities.
Everyone knows from experience how a dreamer will transform one piercing sound, for example, that of a bell, into another of quite a different nature, say, the report of cannon. In his dream he becomes aware first of the effects, which he explains by a subsequent hypothesis and becomes persuaded of the purely conjectural nature of the sound. But how comes it that the mind of the dreamer goes so far astray when the same mind, awake, is habitually cautious, careful, and so conservative in its dealings with hypotheses? Why does the first plausible hypothesis of the cause of a sensation gain credit in the dreaming state? (For in a dream we look upon that dream as reality, that is, we accept our hypotheses as fully established).
I have no doubt that as men argue in their dreams to-day, mankind argued, even in their waking moments, for thousands of years: the first causa, that occurred to the mind with reference to anything that stood in need of explanation, was accepted as the true explanation and served as such. (Savages show the same tendency in operation, as the reports of travelers agree).
Nietzsche, Human, All Too Human