This is another of my short texts originally written a couple years ago in Polish and now translated for sharing here.
I got so used to the idea of Platonic entities that it did not even occur to me to question the widely recognized dichotomy of the concept of existence. After all, it is obvious that I mean different things when I say that there exists a number called four and when I note the existence of a chair on which I sit, right?
And yet, to my own surprise, I find that this distinction gradually slips away from me. At first I did not take it seriously: knowing that the chair consists mostly of an empty space in which unimaginably small particles are arranged, does not make the chair less concrete and tangible.
The first seed of doubt may have been for me the observation that the particles are in constant motion and every second many of them move from the chair to the surrounding air, as well as the other way round. Some of the components change, but the whole remains what it is, at least in my understanding.
What I at first considered to be a truly material thing turns out to be to some extent an abstraction. It is more pronounced in the case of biological entities, such as the human body. Eating and excreting, throughout our lives we constantly exchange particles in our bodies for other - similar, and in principle indistinguishable. Cells die en masse and are replaced by new ones - the only thing that remains unchanged is the general structure.
One analogy I found convincing is that of a standing wave. If one driver suddenly brakes in a long column of cars, a peculiar traffic jam may persist for some time, where every next car has to slow down only because the one in front of it has done the same, although the original cause is not there anymore. Such wave of braking is a property of how the cars move and I perceive it - paradoxically - as something ephemeral and tangible at the same time.
Science convincingly suggests that not only in the case of our bodies, but also our minds, the structure that binds the components is what is important, while the building blocks might be replaceable. It seems possible that in the future we will be able to simulate the operation of the whole brain in a suitably powerful computer. It would not be made of "real" particles, only their digital equivalents. However, the relations between these simulated elements would be subject to the same rules as in our reality - so the structure composed of them would behave in the same way.
For the time being, a simulation of the reality and the minds that inhabit it remains only a fantasy - contemporary computers might be able to accurately represent behavior of complex molecules, but there is still a long way to go to simulate something like an animal cell.
On there other hand, some suggest that perhaps we all live in such a simulated world. When I hear it, a question arises in my mind: would that make any difference to us? After all, what we are able to observe are just the relationships between different components of reality. Each, even the simplest physical interaction that we can perceive is just a fragment of the web of interdependences connecting components of our world. Is it possible to say that one building material would be more "real" than another if both behave exactly the same and we do not even have a theoretical possibility of distinguishing them?
The water molecules behave the same in my body regardless of whether they come from a river, ocean or glacier. If we are able to differentiate them somehow, it is only because their origin in itself is a structure that stretches through time and space - the path that the water has taken from the source to my mouth and beyond, into my cells.
I think that in such a case talking about a building material is at least useless and even illusory. For my existence it is only important how elementary particles are connected, not what they "are" (whatever it means). If someone had copied me and the whole world around me into a simulation at this point in time, from my point of view I would have existed exactly the same as before - as long as that structure of everything was faithfully reproduced.
It would still be me, just as the number two is the same regardless of whether we look at two atoms, two stones or two planets.
Would I equate my own existence with the existence of a mathematical idea? Does it sound absurd? Why?
Thomas Aquinas, inspired by Aristotle, distinguished two components of every being - the essence and the existence. It might be an abuse of these concepts if I claim that what he called "essence" is the structure of a thing in the sense discussed above - because for Thomas Aquinas it was supposed to determine the uniqueness of each being, which I have just questioned. On the other hand, my being is not only the inner structure of my body and mind, but also the whole network of connections between them and the rest of the world in which I am immersed - the reality in which I exist. Within the framework of everything that is observable for us, I am indeed a unique entity.
So what is the second part, the "existence"? When I say that there is a chair underneath me, I mean that its structure is weaved into a huge network of connections that make up the whole world. But I could also try to imagine the same chair in a separate, fictitious reality - and then it would really exist in a different way because it would be a part of a different structure.
It is not surprising that we attribute a special kind of existence to things that are entangled in the same structure as we are: in our universe, which is a web connecting everything from the beginning until the end of time. Even time as such exists in this sense - it is a special kind of relation between all the elements of our reality.
Is it possible that we distinguish this universe - which could even be a purely mathematical construction - just because we are part of it? Any hypothesis we might have at this point would be, I think, unfalsifiable. After all, we can only observe things that exist in the same sense as us - that is, ones that are part of the same world. Our world.