∃x?

I was in the cathedral today, staring at the ceiling. Turquoise and gold, some brown and red. The birth of Jesus, the healing of the blind man, children crying and the pope rambling about the Bible amongst speaker static. My mind was not with God at that point, but with Existence. Perhaps they are the same. I guess I'll only know at the end. Certainly, the end is the only certainty. Forever is an illusion. The Universe popped out of a tiny spot, and it will either end compressed in that tiny spot again, or, by the looks of it, will simply die. Like a human. It will become cold and unmoving and dead. Death makes no distinction, it comes for all of us, for everything and everyone all the same.

This is nothing new. We all know we're here one day and then we're not. We've all crushed our fair share of bugs. We've all tasted death. But we're still here and we're so alive. Aren't we? We think, therefore we exist. Don't we?

Existence is an assumption. Once we have established that, everything is fine. Proceed to build up speech, logic, number systems, the wheel, agriculture, prostitution, quantum mechanics and banana bread. It all works out. But is existence always a valid assumption? I would argue no.

Imagine an atom, floating somewhere in a perfect vacuum. There is absolutely nothing around. There can be no interaction between this atom and anything in its vicinity. So, is the atom really there? Perhaps if it has consciousness it can acknowledge its own existence. But what good is that? It would still have nothing to do in this empty space. This is essentially the same as non-existence. However, once our spaceship comes around and we point our handy scanning tunnelling microscope at it we find out, due to the interaction between the atom and the atoms of the microscope's probe, that there is indeed an atom there. All alone, floating in empty space. Except, now we're also in the picture

Interaction is the ability of something to influence or perceive something else   (1)

Existence requires interaction. Or perhaps, an overseeing God is enough. If we postulate that God looks upon us at all times, from some higher dimension or an invisible cloud up above, or a fishing chair on a veranda, this interaction is enough to guarantee our existence. Victory! Now we can make banana bread! But if not, and some people would claim there are plenty of reasons to refute this postulate, then existence is not guaranteed intrinsically, since interaction requires, at a minimum, two parties. The universe is, by definition, the superset of all existing things. It is nothing more than a bag which fits planets, stars, humans, dust, and all that. Hence, we cannot talk about a universe without at least two things in it. So yes, you might be able to get away with saying you're the centre of the universe. If you were floating alone in a vacuum (and let's consider for a moment that you hadn't already exploded) you would be the universe - a collection of interacting particles.

Given the definition in (1), x exists if and only if it interacts with at least one y. The "if and only if" is justified due to the fact that interaction can be viewed as a symmetric relation. Hence, if x interacts with y, y must also interact with x. Two birds with one stone! We have now guaranteed the existence of both parties involved. This relation need not be transitive and is clearly not reflexive. If x interacts with y and y interacts with z, it is not guaranteed that x interacts with z. However, all three elements exist, since a single interaction suffices. As for reflexivity, it is clear that x cannot interact with itself as an interaction requires a minimum two parties, as mentioned previously.

Non-existence is usually taken to mean something that is unphysical but can be imagined. This hints to the fact that there is a hierarchy of existence. The super-existence of imagination, which contains the power set of all existing things, is clearly the most inclusive. One can think of a pink horse with a croissant protruding from its forehead, but this does not mean it exists. Each element, the colour pink, the horse and the croissant has been perceived by the thinker in his or her life, and therefore, the combination is allowed. Another, perhaps more abstract example, is that of the existence of mathematical solutions to the equation governing the projectile motion. This is a quadratic equation which, when solved for the time spent airborne, usually admits two solutions, as per the well-known "abc formula". Sometimes, one of these solutions can be negative, which makes no physical sense as time is defined to be positive. Our experience of physical time is its unidirectional flow towards the future. In this sense physical existence is more restrictive than mathematical existence, and thus a hierarchy of existence is created.

This relationist view of reality is shared by a few prominent names in science, such as Carlo Rovelli, whose weak realism aims to solve the big problems of quantum physics. A popular critique to this view is metaphysical realism, which essentially treats existence as an assumption. Previously, the case in which this works has been explored and resulted in a somewhat uninteresting conclusion. Yes, God is boring. But it goes beyond that. Metaphysical realism claims the reality we are all so familiar with, the reality we study and make models of, the reality in which we drink beers and party and are at war, is a mere illusion, a show put on by our brains. A form of mass psychosis perhaps? Regardless, beyond this there is a fundamentally unobservable reality, to which we will never have access due to our physical limitations.

While it is true that we will never be able to perceive anything beyond our biological limitations, I believe we are ultimately unimportant to existence and reality. I am not needed for the Sun and the Earth to exist. The mere fact that the Earth orbits around the Sun due to the non-zero curvature of space-time is enough for these two objects to exist. Regardless of whether they are conscious in any sense. The action and reaction are an interaction, and interaction is the only prerequisite to existence.

But now the most important question of all, why should we care? Clearly, we're all just out here going about our day, running errands, doing our jobs, eating and sleeping. This is existence. And whether there is something more to it that is unattainable does not have any impact on our routines.

Isn't it nice, though, to feel like you have it figured out? Perhaps this too is only an illusion…

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Carlos de Haes, The Pass. Jaraba de Aragón, Ca. 1872