Philosophy
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Day 4: Does the Future Already Exist?
Yesterday I left you with a question, today we are getting stuck in. If the block universe is right, and my death is already sitting in the loaf at coordinates I haven’t reached yet, then in what sense am I choosing anything?
It turns out this isn’t a new problem. People were freaking out about it 2,400 years ago.
Aristotle’s Sea Battle
Around 350 BCE, Aristotle wrote a short text called On Interpretation. Most of it is dry logic. But in Chapter 9 he stops to consider something that has been bothering philosophers ever since.
Imagine someone says: “There will be a sea battle tomorrow.”
Is that statement true right now?
It seems like it has to be either true or false. That’s basic logic. A statement and its negation can’t both be true. One of them has to be the case.
But if it’s true right now that there will be a sea battle tomorrow, then the sea battle is already locked in. The admirals can deliberate, the sailors can train, the ships can be prepared or not prepared, but the battle is happening, because the statement was true before they did any of that. And if the statement was false right now, then no matter what anyone does, no battle is possible. Deliberation is pointless either way.
This is the original fatalism problem. Aristotle didn’t have a block universe yet. He didn’t need one. He just noticed that if statements about the future already have truth values, the future is already decided.
His escape was to say: future-tensed statements don’t yet have truth values. They become true or false as time passes. The statement “there will be a sea battle tomorrow” isn’t true or false today, it just isn’t yet. Today’s truth is silent on tomorrow’s events.
That’s a tidy answer, and most philosophers since haven’t bought it. Bivalence, the idea that every proposition is either true or false, is hard to give up.
The Block Universe Version
Fast forward 2,300 years. Einstein hands us the block universe. Now we don’t need to worry about statements, we can talk about the actual thing. Tomorrow’s sea battle is sitting at its spacetime coordinates whether anyone says anything about it or not. Tomorrow’s you is sitting at its spacetime coordinates whether you’ve made up your mind or not.
So when you sit down at lunch and choose between the salad and the pizza, is anything actually being decided? Or is the salad-eating version of you already there in the loaf, and your “deliberation” is just the part of the loaf where the neurons fire?
This is the worry that makes the block universe feel like a horror movie.
Compatibilism, or: It’s Not as Bad as It Sounds
The standard response is associated with philosophers J.J.C. Smart and David Lewis, and it goes like this.
Yes, the future is fixed. But “fixed” isn’t the same as “forced.”
When we say tomorrow’s you eats a salad, what does that mean? It means tomorrow’s you deliberated, weighed the options, and chose the salad. The block universe doesn’t bypass your decision. Your decision is what’s written into the block. The reason the future slice shows you eating a salad is because the present slice, the one doing the deliberating right now, picks the salad.
You are not a passenger on a fixed track. You are part of the track-laying. Your choosing is a real causal node in the structure, not a piece of theater performed over a predetermined script.
Compare it to the past. The past is fixed too. Yesterday’s choices are locked in. We don’t usually feel like that’s a problem, because we remember making them. The block universe says the future has the same status as the past, with one difference: you don’t remember it yet.
This doesn’t fully comfort everyone, and I get it. The libertarian objection, made forcefully by Peter van Inwagen, is that genuine free will requires the ability to do otherwise. If the block already shows you eating a salad, there’s no sense in which you could have eaten pizza. Counterfactually, sure, in a possible world where your desires were different, you’d pick pizza. But in this world, the salad is already there. The pizza branch was never on the menu.
I find the compatibilist response more convincing than the libertarian one. But I also notice that I would say that, because I want to keep eating salad and feel like I picked it.
Quantum Mechanics Isn’t Going to Save You
A lot of people, when they first encounter this problem, reach for quantum mechanics. Surely the universe is fundamentally indeterministic at the smallest scales. Surely that means the future isn’t fixed, that quantum events ripple up into our brains and give us real openness.
This rescue doesn’t work, and the reason is sharp.
If your decision to eat the salad was caused by a random quantum event in your brain, then your decision was random. Randomness isn’t agency. If a quantum fluctuation makes your arm jerk and you punch someone, you didn’t choose to punch them. You twitched.
Indeterminism gives you unpredictability. It doesn’t give you authorship. Free will, if it means anything, has to mean you did it, not that a die was rolled inside your skull.
Some philosophers like Robert Kane have tried to thread the needle here, proposing that quantum indeterminism happens at moments of intense deliberation, and that the agent’s “effort of will” resolves the indeterminacy. I find this hard to believe, because it just relocates the mystery. How does the effort of will resolve the indeterminacy? If we knew, we’d be done. We don’t.
Tomorrow is not today’s set of problems, because today’s problems are in the process of being solved.
Sources
- Future Contingents - Stanford Encyclopedia of Philosophy (Aristotle’s sea battle)
- Fatalism - Stanford Encyclopedia of Philosophy
- Compatibilism - Stanford Encyclopedia of Philosophy
- Peter van Inwagen - Wikipedia (author of An Essay on Free Will, 1983)
- Robert Kane - Wikipedia (author of The Significance of Free Will, 1996)
- J. J. C. Smart - Wikipedia
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Day 3: Einstein Made Us A Loaf
When Albert Einstein’s lifelong friend Michele Besso died in March 1955, Einstein wrote a letter to Besso’s family. In it, he wrote one of the most quoted sentences in the philosophy of time:
“People like us, who believe in physics, know that the distinction between past, present, and future is only a stubbornly persistent illusion.”
Einstein died a few weeks later.
What he was pointing at has a name now. The block universe.
The 4D Loaf
The block universe says reality is a four-dimensional structure. Three dimensions of space, one of time, stitched together into a single thing. Every event that ever happened, that’s happening, that ever will happen, all of it exists. Equally real. The Big Bang is over there in one corner of the loaf. The heat death of the universe is at the other end. Your tenth birthday is somewhere in the middle. Your death is somewhere too.
Nothing flows. Time doesn’t pass. The loaf just is.
This sounds insane. It is also where the math points.
Why Physicists Buy It
The argument is special relativity, and once you see it, it’s hard to unsee.
Einstein showed that simultaneity, the idea that two events happen at the same time, depends on how you’re moving. If you and I are at rest with respect to each other, we’ll agree on what’s happening “right now.” But if I get on a train and you stay on the platform, my “now” and your “now” start to disagree. Events you consider simultaneous, I won’t. And not because either of us is wrong. We’re both reading our clocks correctly. The universe just doesn’t have a single shared “now.”
Take that one step further. If my present and your present can disagree, whose present is the real one? Mine? Yours? Some third observer’s? The only answer that doesn’t pick favorites is: all of them. And if all of them are equally real, then the past and future they each describe must also be real, because one observer’s future is another observer’s now.
Philosophers Hilary Putnam and C.W. Rietdijk worked this out in the 1960s. Their argument, roughly: if my “now” overlaps with your “now,” and your “now” overlaps with someone else’s, and that someone else’s “now” overlaps with an event in my future, then by transitivity that future event exists right now. Not metaphorically. Actually exists.
Therefore, if you take special relativity seriously, the future is already here.
“Now” Is Just “Here”
The block universe has a clean way to talk about what feels like flow. “Now” works the same way “here” does.
“Here” doesn’t pick out some metaphysically special location in space. It just means the place I am. Other places are equally real, even though they’re not here. New York exists when I’m in San Francisco. I don’t need to be there for it to be there.
“Now” is the same. The moment I am. Other moments are equally real, even though they’re not now. 1955 exists when I’m in 2026. Einstein doesn’t need to be alive for 1955 to be a real place in the loaf.
This view is called eternalism: past, present, and future, all equally real. It’s the natural ontology of the block universe, and most working physicists, when asked, will admit they think something like this.
The Objection That Doesn’t Go Away
There’s an objection, and it’s the one your gut has been making since the first paragraph.
It doesn’t feel like a block. It feels like time flows. It feels like the present is special, the past is gone, and the future is open. We make choices. We anticipate. We regret. None of that lines up with a frozen 4D loaf where everything is already written.
Philosophers who take this objection seriously are called presentists. They say only the present is real. The past was, the future will be, but right now only this moment exists. This is closer to common sense, but it has a hard time with relativity. If only the present exists, whose present? The presentist owes us an answer, and most of the answers involve denying relativity in ways physicists find suspicious.
For today, the block universe gets to make its argument unopposed.
Rovelli’s Wrinkle
Carlo Rovelli I think mostly buys the block? He doesn’t think there’s a fundamental flow. He’s also not satisfied with leaving it there.
If there’s no flow at the bottom, why does it feel so vividly like there is? His answer is emergence. Flow is real the way temperature is real. There’s no such thing as the temperature of a single atom. Temperature emerges when you have a lot of atoms, statistics, and a viewer who’s coarse-grained enough to perceive averages instead of individual particles. Time’s flow, in Rovelli’s view, is similar. It emerges from entropy, from our memory pointing one way, from our being the particular kind of system we are.
That isn’t an answer that satisfies everyone. The philosopher Tim Maudlin has spent decades arguing that fundamental temporal passage is real, that the block universe view throws away something that ought to stay. I’m sympathetic. But Maudlin is not, today, winning.
So What Does This Mean For Me?
Here is the question that should have been tickling that noggin.
If the block universe is right, if my death is already sitting in the loaf at coordinates I haven’t reached yet, then in what sense am I choosing anything? If my actions tomorrow are already there, written into the geometry, am I just walking down a track that’s been laid?
But that’s tomorrow’s past, sorry, post.
Sources
- Being and Becoming in Modern Physics - Stanford Encyclopedia of Philosophy
- Time - Stanford Encyclopedia of Philosophy
- Rietdijk–Putnam argument - Wikipedia
- Michele Besso - Wikipedia (source for the Einstein letter quote)
- The Order of Time - Wikipedia (Carlo Rovelli, 2018)
- Tim Maudlin - Wikipedia (author of The Metaphysics Within Physics)
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Day 2: A Philosopher Argued Time Doesn't Exist
In 1908, a British philosopher named J.M.E. McTaggart published a paper called “The Unreality of Time.” The argument is exactly what it sounds like. He thought he had proven, with logic, that time is an illusion. Not “feels different than we think.” Not “isn’t fundamental.” Unreal.
Almost 120 years later, people are still arguing about whether he was right. People have written entire dissertations on McTaggart, and yet here I am trying to reduce his paper to a blog post. I’ll do my best to make it make sense.
Most modern philosophers think the argument fails, but the way it fails that matters. McTaggart carved up the conceptual landscape that every philosopher of time has been working in since. If you want to argue about time at all, you’re using his vocabulary, even if you’re trying to refute him.
Two ways to talk about time
McTaggart starts by noticing something obvious once you see it: there are two different ways we order events in time.
The first way is fixed relationships. The Battle of Hastings was earlier than the moon landing. The moon landing was later than the Battle of Hastings. These facts will be true forever. The relationship doesn’t change. He calls this the B-series.
The second way is changing properties. The moon landing used to be in the future. Then it was in the present. Now it’s in the past. The event itself didn’t change, but its tense did. He calls this the A-series.
You use both every day without noticing. “I have a meeting at 3pm” is B-series, it’s at 3pm whether you say it on Monday or next year. “I have a meeting in two hours” is A-series, that statement was true at 1pm and false at 4pm.
So far, no philosophy emergency. Two ways of describing time. Cool.
The argument
McTaggart’s argument has two steps, and the trick is how they trap each other.
Step one: For time to be real, you need change. Stuff has to actually become other stuff. Without change, you don’t have time, you have a frozen catalog of events. Fair enough.
Step two: The B-series can’t give you change. The relationship between Hastings and the moon landing never changes. Nothing in the B-series ever becomes anything else. It’s a static ordering.
So if you want change, you need the A-series. Events have to actually move from future to present to past. That’s where the change lives.
And this is where it gets weird. The A-series is contradictory.
Every event in the A-series has to be past, present, and future at some point. The moon landing was future before 1969, present on July 20, 1969, and is now past. So it has all three properties. But past, present, and future are incompatible. An event can’t be all three.
The obvious response: well, it has those properties at different times. Future first, then present, then past. Not all at once.
McTaggart was ready for that. If you say “at different times,” you’re using time to explain time. You’ve assumed the thing you’re trying to define. The A-series was supposed to be what makes time real, and now you’re using time to fix the A-series. Circular.
So: change requires the A-series. The A-series is contradictory. Therefore no change, therefore no time.
Does it work?
Mostly people think it doesn’t. But the responses split into camps that are still arguing.
Some philosophers say the A-series is real and McTaggart’s contradiction objection is bad. They’re called A-theorists. They argue that having different temporal properties at different times isn’t circular, it’s just what time means.
Others say the B-series is enough, and you don’t need real change in the way McTaggart thought. The “change” we observe is just a feature of how we experience the sequence. They’re called B-theorists. To them, the moon landing being past from where we sit and future from where Buzz Aldrin sat in 1968 are both just facts about a four-dimensional structure that doesn’t itself move.
I’ll get into this in more detail in the next post, while trying to tie it back to Rovelli’s work on time.
Actually, hang on a minute, this is my post.
McTaggart Was Right All Along
He noticed that we use two different vocabularies for time, and we never worked out how they fit together. We just slide between them depending on what we want to say.
That sliding is everywhere once you notice it. “It’s been five minutes.” B-series. “I’ll do it tomorrow.” A-series, scoped to “now.” “I have a 3pm.” B-series. Sometimes in the same sentence, two different ways we think about time.
Rovelli argues that the features we associate with time are emergent. They don’t exist at the subatomic level. Time runs differently in different gravitational fields, which is strange if time is supposed to be a fundamental property of the universe rather than something that arises from how we observe it.
Therefore, time is a human construct, and a British philosopher figured it out in 1908.
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30 Days of Time
I’m a big audiobook guy. Ear reading instead of sight reading, as I like to call it. Lately I’ve been ear reading The Order of Time by Carlo Rovelli, and it has wrecked me in the best possible way.
Rovelli’s argument, roughly, is that a uniform, universal flow of time does not exist at the fundamental level. The features we associate with time, a direction, a presentness, a duration, are tied to our perspective and to thermodynamics. We don’t fully understand the microstate of the universe and his argument is that the flow of time isn’t even there to be known. That’s a hell of a thing to think about when sitting in traffic between two city buses on your way to picking up fried chicken for dinner.
So I got curious. Not just about the physics, but about all the neighboring topics. Calendars. Daylight Saving Time. Leap seconds. The fact that GPS satellites have to correct for relativity or your maps app stops working. The fact that Mars uses its own day. The fact that we voted in 2022 to abolish the leap second by 2035, and most people did not notice.
I’ve decided to spend the next 30 days writing about it. One post a day. Welcome along.
The shape of the series
I don’t want to spoil the destination, so I’ll just sketch the journey. The series breaks into four rough movements, one per week.
Week 1 — What time is. The philosophy is older than the physics. Does time flow, or is it a frozen 4D block we move through? Why does your brain experience “now” the way it does? Do other animals even live in the same time you do? This is the squishy, weird, fun stuff. No equations, lots of questions.
Week 2 — How we measure it. Sundials to cesium to optical lattice clocks. The second is a defined unit now, and that decision had consequences. We’ll talk about why your phone’s clock is more accurate than any clock that existed when your grandparents were born, and what that accuracy is for.
Week 3 — How computers handle it. Unix time, NTP, ISO 8601, time zones, DST. The infrastructure quietly holding the digital world together, and the bugs that fall out of it twice a year. If you’ve ever shipped code that broke at 2 a.m. on the second Sunday of March, this week is for you.
Week 4 — Where it breaks. Leap seconds, calendar reform, DST politics, the slow drift between atomic and astronomical time. The current system is more held-together-with-tape than most people realize. By the end of the week I want us both asking the same question.
I’m not going to tell you what that question is yet. Part of the fun is getting there together.
What this is, and what it isn’t
This isn’t a textbook. It isn’t a research project or a reading log either. It’s a series of posts on a topic I’m interested in.
I’m not a physicist, so I’ll do my best to make sure the posts aren’t wrong. If you spot a correction, replying on Mastodon is the best way to let me know.
Why 30 days? Why not? I may do more later if a particular topic wants more room. But 30 days on a single subject is probably enough for most people who show up here for programming posts. Instead, you’re getting a 30-day divergence into physics, astrophysics, and a little philosophy. Week 3 covers computer time, so there’ll be some programming in there. Just not a lot of it for a month.
My research notes live in an Obsidian vault. I’m keeping them private for now, but I may share more by the time the series wraps.
How to follow along
New post every day for 30 days, starting now.
RSS is the easiest if you want every post as it lands. Email is a weekly digest, good if you’d rather catch up on Sundays than see every post the moment it drops. Mastodon is where each post lands on social, and any replies there show up back on the blog as comments: @[email protected].
Pick whichever annoys you least.
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The universe is a giant board game. Space is the board, matter is the pieces, and logic is the rules. Language is our rulebook of how we describe how the board works. You can’t separate the rules from the board; if you had a different board, the rules would be different too.
When you get to the “what ifs,” it becomes a thought experiment, not grounded in science.
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Transhumanism (as a fictional genre, not as a philosophy) is about the idea that we can use technology to overcome the problems inherent to human nature, while cyberpunk is about the idea that we can’t.
I propose a new form of philosophy called “Cyberpunk Luddism.” The idea comes from reading a blog post on Kagi Small Web about Molly’s Guide to Cyberpunk Gardening. In it, they mention the interesting quote above, that I have tracked down the original source from 2009. Stephen Lea Sheppard on RPG.net