Frequent readers of my blog will probably notice a theme emerging, posts named "Does \(X\) exist?" for a growing number of values of \(X\). Why should anyone care? Because the inquiry into similar questions, like whether or not God exists, can benefit from this exercise. The stakes feel lower when we discuss the existence of time, or of mathematical objects. These lower stakes can remove some psychological barriers to reasoning about this question, and then we can use what we learned when we think about the bigger questions. I will make amateur ontologists out of you all! (Ontology is the study of what exists, it's a branch of metaphysics).
Another reason I wanted to write this is that my obsession with the nature of time led me to God. I started out as an atheist. I always assumed a materialist metaphysics, which takes only the objects of physics to be real. Only particles and spacetime are real. Everything else is either assumed to be fake or ultimately is reducible to particles existing in some subset of spacetime.
But even within physics, there's still an unsolved problem of what time is. I explored it in my 2020 post "Time in Physics". That post contrasts the two dominant ideas: Eternalism and Presentism. Eternalism says all times, past, present and future, exist in a spacetime manifold. That manifold is a single static structure, and it's simply a property of "Self-Aware Substructures" of the manifold that they experience their here-nows as "now". The way entropy works makes any information-processing substructure experience only one direction of movement through time. In Eternalism, it's like Copernicus' paradigm-shift for space. Copernicus made a simpler model of the orbits of planets by not assuming the earth was a special point. Eternalism is Temporal Copernicanism.
By contrast, Presentism is anti-Copernican, in that it posits that the present really is a special moment in time. The reason this is more justified than the equivalent Copernican view about space is that we can't arbitrarily move through time the way we can through space. We do seem to be inexorably dragged through time. This idea is explored in depth in Lee Smolin's book Time Reborn.
Presentism vs Eternalism have some implications about the possibility of time travel. In Eternalism, time travel is possible since all the past and future moments are just as real as the present moment, so it makes sense to travel to them. But in Presentism, past moments are gone, and no longer exist. Future moments are yet to come, so they don't exist. This is not a new idea, St. Augustine of Hippo wrote this in 400 AD in The Confessions, book 11:
Another reason I wanted to write this is that my obsession with the nature of time led me to God. I started out as an atheist. I always assumed a materialist metaphysics, which takes only the objects of physics to be real. Only particles and spacetime are real. Everything else is either assumed to be fake or ultimately is reducible to particles existing in some subset of spacetime.
But even within physics, there's still an unsolved problem of what time is. I explored it in my 2020 post "Time in Physics". That post contrasts the two dominant ideas: Eternalism and Presentism. Eternalism says all times, past, present and future, exist in a spacetime manifold. That manifold is a single static structure, and it's simply a property of "Self-Aware Substructures" of the manifold that they experience their here-nows as "now". The way entropy works makes any information-processing substructure experience only one direction of movement through time. In Eternalism, it's like Copernicus' paradigm-shift for space. Copernicus made a simpler model of the orbits of planets by not assuming the earth was a special point. Eternalism is Temporal Copernicanism.
By contrast, Presentism is anti-Copernican, in that it posits that the present really is a special moment in time. The reason this is more justified than the equivalent Copernican view about space is that we can't arbitrarily move through time the way we can through space. We do seem to be inexorably dragged through time. This idea is explored in depth in Lee Smolin's book Time Reborn.
Presentism vs Eternalism have some implications about the possibility of time travel. In Eternalism, time travel is possible since all the past and future moments are just as real as the present moment, so it makes sense to travel to them. But in Presentism, past moments are gone, and no longer exist. Future moments are yet to come, so they don't exist. This is not a new idea, St. Augustine of Hippo wrote this in 400 AD in The Confessions, book 11:
The only thing that we can call the present is an instant of time, which we might conceive as an indivisible particle made up of no subdivided moments. And yet this present particle flies with such great speed from the future to the past that it has no length at all. For if it did, it would be divided into past and future, but the present takes up no space
He did this after reasoning through how you can't even say that an interval of time "is long" because it consists of moments which span both the future and the past. So you can either say the interval of time "will be long" or "was long", but then he even refutes that, since you cannot measure what does not exist. He takes only things in the present to have the property of existence. He was a Presentist, and he was trying to square this with his belief in a transcendent God, to whom the past, present and future all exist. He was struggling with this same tension.
What Augustine was trying to figure out is how God, who is eternal and outside of time, came to create the world, which had a beginning, has a present, and will have an end. He doesn't figure it out, and is essentially writing a letter to God to ask for guidance. But in actively struggling with the nature of time, he's seeking God. This intersection of the eternal and the temporal is The Question, in my view. Augustine knew.
The reason I brought in both physicists and theologians is that I think both can contribute to this inquiry. Theologians understand the purpose of time and our boundedness in it, but physicists can sharpen and make many of the "how" questions precise and tractable. But they both run into this Presentism/Eternalism conflict. It's a deep, unsolved question and we all should think about it more.
Time is mysterious. It's also important, time is money, time is precious. Time exists, it must exist, we exist in it, and we exist. We must use it well, and really live in time, in order to grow and become the kind of person who can eventually transcend it. It's worth struggling with this question and really taking it seriously. Time is both the most natural, familiar thing, and also the most alien, anomalous thing. Is it even a thing? Is it a river? Is it a flat circle?
The first gulp from the glass of natural sciences will turn you into an atheist, but at the bottom of the glass God is waiting for you.
- Werner Heisenberg