Let me try an answer (half-baked thoughts, I admit, but writing this article helps me to clarify them). One answer would be: it exists because you, the reader, can interact with it through a number of operations. You can open it, scroll etc. That interface is the set of all operations you can perform on this post (including reading it).
The blog post is implemented in terms of some “lower level” objects (programs, data structures etc.) which in turn are implemented in terms of something more basic. Those “lower levels” could be exchanged without exchanging the properties of the blog post as it exists from your point of view. From the point of view of the reader or observer, they do not exist (or they exist behind a “horizon”).
However, the blog post does not have an independent existence, independent from you or other observers interacting with it. The data, stored on some computer system, are there, but as a blog article, it only starts to exist on your screen and in your perception.
But what about you, the reader, the observer? Maybe we are also implemented in terms of lower levels. So maybe what we have here is an observer implemented in terms of low level objects (like, for example, neurons and neuronal signals). But just like the electronic components or the statements of program code do not exist from the point of view of the reader of a blog post, the neurons and neuronal signals do not exist from the point of view of the observing system implemented by them. They are behind a horizon of accessibility, so to speak.
But just as the blog article exists by being observed, the observer also exist by observing him/her/itself. It therefore has an independent existence (although it depends on its implementation in terms of the “underlying” system). It seems to me that consciousness is the reality of that existence. Reality does not just consist of objects on a lowest level. Reality consists of entities on different levels of description. The “higher” levels of description are real by being observed by observers and what gives them reality is that the lower levels (the ones implementing them) are hidden from the observer’s view because the observer interacts with them through an interface that does not provide access (or information) about these lower levels. Just like you see this article as an article, not as a set of programs on some computer system. A conscious system is observing itself and by doing so, becomes real from its own point of view. From its own point of view, it is a basic entity with directly existing properties, instead of being a bunch of parts.
It is real, but it is not basic if you look at it from the outside. From the outside, you only see the neurons and the signals they are sending, or the molecules. Or you observe something like the words uttered by that system, but that is not the same interface the system has onto itself. You can, however, perceive the other as a human being and simply ignore the neuronal or physical view.
From the observing system’s own point of view, it is the only really real thing. It can postulate the existence of an outside world or of an underlying system implementing itself, but that is a hypothesis. This situation also exists in the blogging example. In the blog post, the programmers and technicians could migrate the blogging platform to another hardware, with a different operating system, with a totally different hardware. Hard drives could be exchanges my flash memory and optical discs. From your point of view, the article would not change at all. The world behind the interface could be this way or that way, who knows. Maybe it’s just magic and no computers at all. You cannot know for sure. The nature of the blogging platform is metaphysics 😉 – you cannot know the thing in itself (except you are a programmer). But even for the programmer, there is a platform he is working on and that platform is accessed through an interface. There is a horizon of accessibility beyond which he or she cannot see. The technician can, but he or she cannot look inside the electronic parts. Ultimately, there is physics (maybe with several layers again).
You can react to this situation in two ways: either, you can ignore anything behind the horizon. You ignore your own implementation (consciousness then appears as something primary that just is. Likewise, the blog article just exists). You just ignore that the world as it appears to you is implemented or emulated by something “beneath” it. You are just describing it as it appears. I do not claim that I understand phenomenology, I know too little about it, but it appears to me that it is something like this the phenomenologists are doing. Some of them might consciously ignore the implementation of the experienced world and concentrate on the “user’s view” of things alone.
Some of them might pretend or even believe that consciousness and the experienced world it is not implemented but it just exists like that. You would then arrive at something that looks a little bit like the physics of Aristotle or that of the Pre-Socratics. This Blog-Article just exists, a table just exists, you just exist, time is experienced time. Fundamental ontology from such a point of view would not be a description on the level of particle physics but a description on the level of the experienced world and the experiencing consciousness. You describe it, but you do not look for explanations. The human world is what really exists. Is it something like this that Heidegger was attempting? I can’t really say, since I cannot claim to really understand him, but maybe.
The other possibility is to assume that there is something behind the horizon, i.e. the experienced world of phenomena and the experiencing consciousness are implemented in terms of some other “world”, and maybe there are other interfaces like programming interfaces or microscopes and electrodes and particle accelerators that can be used to look under the hood. I, for my part, am interested in the implementation as well. As a programmer, I am used to look at both the user’s view of the system and the implementation of it. The implementation is hidden from the user since the user should not be required to know anything about physics, electronics, programming or the like. He interacts with an object like a blog article or an app or whatever, just like he interacts with a car or a table. But there is something under the hood, in that computer system as well as inside my head.
I do not, however, believe in reductionism, at least not in the normal sense of that term. The reason is that the description of the implementation of an implemented system may be incomplete in principle since that system can be modified or can modify itself. The implementation of some things can also be exchanged or modified. The implemented system is the product of an evolution that consists of such modifications. So even if you had a complete theory describing the downmost level, you would not have a complete theory of everything. But that is outside the scope of this article.
Ontology, from this point of view, is not only the description of the experienced world (or the user’s view or user interface or the self-experienced consciousness) but the description of how these phenomena are implemented in terms of a underlying system (which might in turn be implemented by something else). A fundamental ontology would then deal with objects on the level of elementary particles or something like that. But these views are not necessarily mutually exclusive.
So in which sense does this blog post exist? It depends on the point of view.
(The picture is from https://commons.wikimedia.org/wiki/File:Moire-(quadrat)-2.png. Looking at such pictures shows that there are processes going on “behind the horizon”. We are trying to create interpretations, but there are several possible ways to group the elements of the picture, so the interpretation is not stable.)