Right now seeing is happening.
Listening is happening also.
Sensations are going on.
And so on.
When we describe stuff it seems separation is a fact. Usually we don't question what we think it's a fact.
But...
I figured you were alluding to this.
I'd actually like both of us to keep a open mind here. Contrary to what you mentioned above, I think most of us traditionally experience all sensory faculties simultaneously. We think that seeing and hearing are happening at the same time, say when driving, it feels like we're paying attention to stimulus coming in all at once. But could it be possible that at a sub-perceptual level, consciousness is actually oscillating very quickly between the different human organ instruments (ear, eye, skin) that is beyond our ability to perceive it that way.
Sight and sound are actually out of sync. Say when listening to a person talk and lip reading. Light travels faster than sound, so visually we are seeing the lips move then the sound actually catches up. This has been measured and is all happening at a sub-perceptual level so it's difficult for us to conceive. And studies have shown it also varies from person to person.
Renowned Meditation Master Mahasi Sayadaw:
"In reality, seeing does not occur at the same time as hearing, nor does hearing occur at the same time as seeing. Such incidents can occur only one at a time. A yogi who has just begun the practice and who has not sufficiently developed his mindfulness, concentration and knowledge will not, however, be in a position to observe all these moments singly as they occur in serial order. A beginner need not, therefore, follow up on many things. He needs to begin with only a few things."
I also recall reading from experienced meditator Culadasa, that the mind is actually conscious of a single event one at a time.
But yes I get it, everything mentioned above is not at my direct experience, it is secondhand information. However, I wouldn't discredit the direct experiences of highly trained meditators who have logged more hours of meditation under their belt. I'm open to the possibility that they can perceive more than the average. Humans can accomplish some pretty remarkable feats both physically and mentally.
I'm also aware, what I mentioned above gets into the concept of time. Which I know doesn't really exist and all things are happening now, despite it may appear things happening sequentially.
If you notice this present experience, as it is, do you see borders separating the seeing, the hearing, the sensing, etc, etc.
Use a finger. Point to the separation you are saying can be experienced. Can you find it? Can you find borders, seams, division?
Is sensing like a puzzle made of separate parts?
You don't necessarily need to "see" borders. This is where it can be very debatable. I "see" the border of my skin separate from the environment, but it doesn't mean I'm actually separate. And to your questions, the borders aren't seen. It is through distinct experiences that the realms of sight, sound, touch, taste, and smell do not cross each other. So yes, I find that it never crosses. I can never taste blue, see bitter, or hear stinky. These are quite different instruments meant to perceive different things, hence separate. Likewise, you can't use a piano to create a painting or a paint brush to produce music.
A blind man will never understand what it's like to see. So how can we say it's not separate from hearing. The blind man will always be missing a piece of the puzzle.