That’s correct. But it’s worth noting that Phenomenology puts forth the idea that there’s both an inner horizon and an outer horizon. Their ideas on the structure of experience differ in significant ways, but both the phenomenologist Aaron Gurwitsch and Ven. Ñanavira break experience down into a tripartite structure.
Every field of consciousness comprises three domains or, so to speak, extends in three dimensions. First, the theme: that with which the subject is dealing, which at the given moment occupies the ‘focus’ of his attention, engrosses his mind, and upon which his mental activity concentrates. Secondly, the thematic field which we define as the totality of facts, co-present with the theme, which are experienced as having material relevancy or pertinence to the theme. In the third place, the margin comprises facts which are merely co-present with the theme, but have no material relevancy to it. We shall endeavor to bring out the type of organization which prevails in each of these domains and determines both the relationship between the data that belong to that domain and its relationship to the two others, particularly to the theme. By dimensional differences between organizational forms we mean differences between types of organization which pertain to, and are characteristic of the three dimensions in which every field of consciousness extends. Each of the above types of organization has a specific formal structure of its own, independent of the organized content and the particular forms of organization, which depend upon the content to some extent. It is the formal structure of these types of organization which will primarily interest us here. With the pattern theme-thematic field-margin, we intend to present a formal invariant of all fields of consciousness. ~ Gurwitsch, The Field of Consciousness pgs. 55 & 56
So the peripheral would be Gurwitsch’s margin, but if we shift our attention to the margin while it does become the foreground, it does so as an “idea” against a more general background of itself. This is how we experience the peripheral as it endures.Now we see that three levels of the hierarchy are involved: on top, at the most general level of the three, we have a thing enduring eternally unchanged; below this, we have a thing changing at regular intervals of one unit of duration, one moment; and below this again, in each of these regular intervals, in each of these moments, we have an infinite series of moments of lesser order accelerating and coming to an end. We have only to take into account an eternal thing of still higher order of generality to see that our former eternal thing will now be changing at regular intervals, that the thing formerly changing at regular intervals will be accelerating its changes (and the series of changes repeatedly coming to an end at regular intervals), and that the formerly accelerating series will be a doubly accelerating series of series. There is no difficulty in extending the scheme infinitely in both directions of the hierarchy; and when we have done so we see that there is no place for anything absolutely enduring forever, and that there is no place for anything absolutely without duration. ~ Ñanavira, FS II
What was once the foreground falls into the background of the inner horizon of the less general and more concrete. In the language of Gurwitsch satisampajañña is shifting our attention from the theme to the thematic field and observing what we are doing as we are doing it, i.e. as it endures in time. This is the “vertical view” at “right angles” to the horizontal that Ven. Ñanavira refers to in his writings. The “theme” is still present, but no longer the focus of attention, i.e. it falls into the background of the inner horizon.The question of self-identity arises either when a thing is seen from two points of view at once (as in reflexion, for example; or when it is at the same time the object of two different senses—I am now both looking at my pen and touching it with my fingers, and I might wonder if it is the same pen in the two simultaneous experiences [see RŪPA]), or when a thing is seen to endure in time, when the question may be asked if it continues to be the same thing (the answer being, that a thing at any one given level of generality is the invariant of a transformation—see ANICCA [a] & FUNDAMENTAL STRUCTURE—, and that 'to remain the same' means just this). SN Attā, emphasis added
But to cut to the point, the mere fact that there is change at all undermines the ontological moorings of the background. And that change is inevitable and beyond our control undermines the notion of self. Citta exists eternally as the most general self-same background of experience, its self-identity unchanged by the appearance (uppāda), the change while standing ( thitassa aññathattam) , and disappearance (vayo) that define it for what it is, but its existence is only relative. Cf. FS I footnote [c]:
The images involved in thinking must, individually at least [though not necessarily in association], already in some sense be given—i.e. as what is elsewhere, or at some other time, or both—at the immediate level, before they can be thought. Perhaps the method of this Note will suggest a reconciliation between the Parmenidean absolute denial of the existence of no thing, with its corollary, the absolute existence of whatever does exist, and the merely relative existence of every thing as implied by the undeniable fact of change. emphasis added