I don't think that experiential psychologists or philosophers of mind would agree with that statement, but it's a very useful perspective if you're doing insight practice. The main assumption is that
only what you consciously experience is real at a given moment.The qualification "conscious" is important here, because from a conventional point of view, it's true that reality appears as sight, sound, smell, tactile sensation etc. simultaneously. What I was getting at is that in noting practice, if you note quite quickly and consistently, you tend to experience the different aspects of reality sequentially, not simultaneously. That is because through noting, you become aware of the extremely fast movements of conscious attention from one object to another, which, if not seen this way, can create the impression of multiple simultaneous sensations. In addition, there is a tendency to see that each senate experience, touch, sight, sound, etc. is followed by a small mental echo, so that experience oscillates between actual sense contacts and the mental impressions these leave in the mind.
That is just what reality looks like when you're doing noting practice, and as the OP is about noting practice, I thought it might be useful to give a hint in that direction. Now one could argue that the impression of there only ever being one sensation arising and passing, followed by a mental echo arising and passing etc. is only produced by the artificial way of looking at reality in noting practice: Are we talking about a feature of reality or a feature of the attention apparatus?
I would argue that one major point of insight practice is to see that for practical purposes, there isn't much difference between the two.
For clarification and further reference I quote a few paragraphs from the MCTB section on impermanence that deal with this perspective:
MCTB:
What do I mean by “experiential reality?” I mean the universe of sensations that you actually experience. There are many gold standards for reality. However, when doing insight practices, the only useful gold standard for reality is your own sensate experience. From the conventional point of view, things are usually thought to be there even when you can no longer experience them, and are thus assumed with only circumstantial evidence to be somewhat stable entities. Predictability is used to assume continuity of existence. For our day-to-day lives, this assumption is adequate and often very useful.
For example, you could close your eyes, put down this book, and then pick it up again where you left it without opening your eyes. From a pragmatic point of view, this book was where you left it even when you were not experiencing it in any way. However, when doing insight practices, it just happens to be much more useful to assume that things are only there when you experience them and not there when you don’t. Thus, the gold standard for reality when doing insight practices is the sensations that make up your reality in that instant. Sensations not there at that time do not exist, and thus only the sensations arising in that instant do exist. In short, the vast majority of what you usually think of as making up your universe doesn’t exist the vast majority of the time, from a pure sensate point of view. This is exactly, precisely and specifically the point. Knowing this directly leads to freedom.
We are typically quite sloppy about what are physical sensations and what are mental sensations (memories, mental images, and mental impressions of other sensations). These two kinds of sensations actually oscillate back and forth, a back and forth interplay, one arising and passing and then the other arising and passing, in a somewhat quick but quite penetrable fashion. Being clear about exactly when the physical sensations are there will begin to clarify their slippery counterpart that helps create the illusion of continuity or solidity: flickering mental impressions.
Coming directly after a physical sensation arises and passes is a separate pulse of reality that is the mental knowing of that physical sensation, here referred to as “consciousness” (as contrasted with “awareness” in Part III). By physical sensations I mean the five senses of touch, taste, hearing, seeing, and smelling. This is the way the mind operates on phenomena that are no longer there, even thoughts, intentions and mental images.
This mental impression of a previous sensation (often called “consciousness” in Buddhist parlance) is like an echo, a resonance. The mind takes a crude impression of the object, and that is what we can think about, remember and process. Then there may be a thought or an image that arises and passes, and then, if the mind is stable, another physical pulse.
Each one of these arises and vanishes completely before the other begins, so it is extremely possible to sort out which is which with a stable mind dedicated to consistent precision and to not being lost in stories. This means that the instant you have experienced something, you know that it isn't there any more, and whatever is there is a new sensation that will be gone in an instant. There are typically many other impermanent sensations and impressions interspersed with these, but, for the sake of practice, this is close enough to what is happening to be a good working model.
