Why Am I Me? Reality's Record Has a Rule for What You Are and No Rule for Which One

Find yourself in a class photo.

It takes half a second. Three rows of kids, your eyes skim the faces, and there you are.

Matching a face is the easy part. Ask the harder question: why is that kid the one whose headache you feel?

Look at what's in the photo. Every kid is made of the same stuff: the same atoms, run by the same laws, wired into the same kind of brain. Everyone else in the picture has headaches you'll never feel, lunches you'll never taste and a view of the camera you'll never get. One of them is you. Physics describes all of them the same way, and nothing in that description marks one of them as you.

So why that one? Why behind these eyes, and not three rows down?

Part 1 said what you are: one of the rhythms the universe never lets go silent. That left a question sitting on the table. Eight billion people, eight billion of those rhythms. Why this one?

It sounds like a question with no answer, the kind you ask once, late at night, and then drop. It has an answer, and each step on the way to it is an exact result.

The short answer

Here's the whole answer in five steps. The rest of this post takes them one at a time and shows how we know each one.

1. Every page of the record rewinds to one starting page. A page is the record as it stands at one moment. Run any history backward, one tick (one step of the process) at a time, and there's only one road back. Everything that rewinds to the same starting page is a lineage: a family tree with that page for its root.
2. Lineages never mix. No tick moves anything from one lineage to another, and each lineage keeps exactly the share it started with, forever.
3. No law points at one. By a law I mean any rule built from the process that writes the record. That process works the same whatever number the loop's running count starts at, whichever clock you call Left and whichever state you call full. So a law can sort lineages into two kinds, lopsided (the clocks start different) and alike (they start the same), and it can never pick out one.
4. The entries can't single one out either. The entries record what changed, never the count, so two lineages that differ only in their starting count write exactly the same entries. A start spread over two lineages, a blend, writes the same entries as a coin flip between them. And no single reading returns "lineage 47."
5. The laws fix what you are, and the start fixes which. Inside a lineage the laws do choose: they keep Part 1's lasting rhythms and throw everything else into coin flips, and you're one of those rhythms. Which lineage your rhythm lives on comes from the start of the record, never from a law. No law did it, and no law can.

Why this matters: it shows where the answer to "why am I me?" lives. It isn't in the process that writes the record. That process can't tell your lineage from infinitely many others like it, so nothing built from it picks you out. The answer lives at the start of the record. And it gives you something solid: no tick moves anything from one lineage to another, so nothing that happens in the record ever moves you onto a different one.

Previously

Here's everything you need from Part 1, in about a minute.

Reality is a permanent record. Every event is an entry, and nothing is ever erased. I draw the record as the Ledger, a thick book with a deadpan face and one response to everything: Noted.

One tiny process writes it. Below the level of atoms, two units pass a bit back and forth. I draw them as two little clocks joined by a loop of wire. Each clock is either full (holding a token) or empty. Every tick, each clock receives what the other was holding, then keeps it or flips it, and the Ledger writes an entry saying which. If one clock began the tick full and the other empty, one unit of flow goes round the loop: a flowing tick. If the two were alike, nothing flows: a silent tick.

Almost everything falls apart. Each clock also has a setting, one of four, so a clock has 2 × 4 = 8 ways to be and the pair has 8 × 8 = 64 ways to start. Silence throws clocks into coin-tossing, and coin-tossing breeds more silence, so 60 of the 64 starts fall into coin flips within three ticks. They end up like Gary, a drummer who flips a coin before every beat. (Gary is not getting the gig.)

Four last. Exactly 4 never go silent. Two are the spin: both clocks flip, and the same unit of flow goes round the loop every tick. Two are the swing: both clocks keep, and the token hops across and back. Each comes with the token starting on the left or on the right. A rhythm that never goes silent has to start lopsided, with one clock full and one empty, because starting alike makes the very first tick silent.

You are one of them. A moment of consciousness is eight ticks with no silent tick, and only those four rhythms deliver that every time. You're a web of these clocks, not one pair, and you are the rhythm, not the body.

Here's the route, on the Ledger's map. I'll stop after each step to zoom out, so you always know where we are, what we've got, and why the next step comes next.

Step 1: Every page rewinds to one starting page

Every page a history can reach has exactly one road back to the page the history started from. (A history is one run of the process, tick after tick.) Here's how we know, with a swing.

First, what's a page? A page is which clocks hold a token right now, plus the loop's count, plus every entry written so far.

About that count. The loop keeps a running total. Each unit of flow that goes round one way adds 1. Each unit that goes the other way takes 1 away. A silent tick changes nothing. The total starts at whatever whole number it starts at: 0, or 7, or minus 40. (The technical name is the loop's flux. I'll call it the count.)

Now the swing. Left starts full, Right starts empty, the count starts at 0, and both clocks are set to keep. Each tick, each clock keeps what it receives, and the Ledger writes down what happened.

Tick 1: Left receives Right's nothing and keeps it, so Left is empty. Right receives Left's token and keeps it, so Right is full. One unit of flow goes round one way, so the count goes up by 1. At tick 2 the clocks are the other way round, so the flow goes the other way and the count comes back down.

Now stand at tick 3 holding only the page: Left empty, Right full, count 1, and three entries. Rewind it.

Rewinding has one answer at every step. The last entry says both clocks kept. Left is empty and kept what it received, so it received nothing, and that's what Right held a tick earlier: Right was empty. Right is full and kept what it received, so it received a token, and that's what Left held: Left was full. The flow went one way, so take 1 off the count. Now do the same with the next entry back, and the one before that.

At every step there was exactly one answer. A flip undoes itself, so does a keep, and the entry says which one happened. When the entries run out, you're standing on the starting page: token on the left, count 0.

Every page a history can reach rewinds this way, whatever settings the clocks had and however the coins landed, because the entry always says what each clock did. So every page has exactly one road back, and one starting page at the end of it.

That has a consequence. Suppose two histories started from different starting pages and landed on the same page. Rewinding that page has to lead back to both starting pages. It can't, because there's only one road. So no page belongs to two starting pages. A coin toss can change which page a history lands on. It can't change which starting page that page rewinds to, because the answer is read off the page itself.

Call everything that rewinds to one starting page a lineage. A lineage is a family tree. The starting page is the root, and every page the history can reach sits somewhere on its branches, with a split wherever a coin toss decides. The whole record is a forest of these trees, and no two trees share a branch.

A starting page has two parts: which clocks start full, and what the count starts at. The clocks have four ways to start: token on the left, token on the right, both full, both empty. The count can start at any whole number, positive, negative or zero. So there are four lineages for every whole number, which makes infinitely many trees.¹

The clocks' settings ride along with the clocks, but they aren't on the page, and rewinding never needs them. Part 1's 64 starts were four lineages with sixteen settings each, all at the same count.

Zoom out. Step 1 is done. Every page rewinds to one starting page, and the pages that share a starting page make a lineage. The record is a forest with no shared branches, four trees for every whole number. Next, and why: a forest with no shared branches can still have things passing between its trees. Step 2 checks whether anything does.

Step 2: Lineages never mix

No tick moves anything from one lineage to another. Each lineage keeps exactly the share it started with, forever.

Here's why. A tick takes a page and writes a new page by adding one entry. Rewind the new page and the first thing you undo is that entry, which puts you back on the page it came from, and from there you follow the same road to the same starting page. So a tick never changes a page's lineage. A history that starts in a lineage stays in it.

A start doesn't have to sit on one lineage. It can be a blend: some of it on one lineage and some on another. (Quantum physics calls that a superposition.) Each lineage holds a share of the start, a number from 0 to 1, and the shares add up to 1.

(If We're All One, Why Can't I Feel Your Headache? works through this same step and calls a lineage a lane, its starting page the first page, and its share its weight. Same things. This post calls them lineages because it follows each one back to its root.)

I'll draw the lineages as jars. The water in each jar is that lineage's share. The jars are a drawing of the real mechanism: ticks stir the water inside a jar and never pour any of it into another.

Say a start puts 30% on "token on the left, count 0" (jar A), 70% on "both full, count 4" (jar B), and nothing on jar C.

So after one tick, or after a million, the jars hold exactly 30% and 70%. The shares at any later moment are exactly the shares at the start. And a jar that starts empty stays empty: no tick puts a drop into it. So the start fixes which lineages a history sits on and how much each holds, and nothing afterwards changes either.

This wall isn't a thick one that keeps most things out. It has no distance in it, no insulation, no noise and no approximation. No page of one lineage leads to any page of another, so there's nothing for a tick to carry across.

(The Ledger notes every entry, and has never once filed one on the wrong tree. Noted.)

Zoom out. Step 2 is done. Ticks never move anything between lineages, every lineage keeps its starting share, and a lineage that starts with nothing never gets anything. Next, and why: the walls keep the lineages apart. They don't say whether a law can single one out. Step 3 asks.

Step 3: No law points at one

The process that writes the record treats every lineage of a kind exactly alike. It can sort lineages into two kinds. It can never pick out one.

To pick out one lineage, a law has to find something that sets that lineage apart. So look at what sets lineages apart, and at what the process does with each difference.

The count. Start the swing at count 0 and the counts read 1, 0, 1, 0 as the ticks go by. Start it at count 5 and they read 6, 5, 6, 5. The entries are the same, the rhythm is the same, and whatever coins get tossed, the odds are the same. The process only ever adds the flow to the count. It never looks at what the count says.

If that sounds familiar, it's the odometer from Did Time Have a Beginning?: the rule "add one for every mile" works the same whatever number the dial started on.

So slide the starting count of every lineage up by 5 at once, and nothing in the process can detect it. The slide sends "token on the left, count 0" to "token on the left, count 5," and every other lineage somewhere else. Not one lineage stays where it was.

The names. Left and Right are only names, as Part 1 said. Swap them and every flow turns round the other way, and the process runs exactly as before. Swap what you call full and empty and every flow turns round too, and the process still runs exactly as before, because it treats a token and an empty clock alike.

Here's what those three changes do to a lineage:

• Adding to the count turns a lineage into one with the same clocks and any other count.
• Swapping Left and Right turns "token on the left" into "token on the right."
• Swapping full and empty turns "both empty" into "both full."

Put them together and every lopsided lineage turns into every other lopsided lineage, and every alike lineage turns into every other alike lineage. The one thing no change can do is turn an alike lineage into a lopsided one. A lopsided lineage's first tick flows, an alike lineage's first tick is silent, and no renaming of the clocks changes that.

Now take a law that wants to pick out a lineage. It's built from the process, so it can't depend on anything these changes alter. Whatever it picks, it picks together with everything those changes turn it into. That leaves four things it can pick, and only four:

• no lineage at all
• every alike lineage
• every lopsided lineage
• every lineage

Never one. Pick one lineage and you've picked infinitely many.

Here's a drawing of the whole situation. You pull ticket 47 at the deli counter. The counter serves every ticket by the same rule, whether the roll started at 1 or at 4,700. It never swaps two tickets. It has no idea which customer is special.

The ticket is a drawing of a lineage, and the counter is a drawing of the laws. Renumber every ticket and the counter doesn't notice. A counter whose rule said "the special customer holds 47" wouldn't survive the renumbering, because after it the rule points at somebody else. The drawing is off in one place: at a deli, someone pulls the ticket. Step 5 comes back to that.

The one bit. So a law built from the process can read exactly one yes-or-no fact about a lineage: does its first tick flow, or is it silent? One bit, and nothing finer.

That bit isn't trivia. It's the first gate from Part 1. A rhythm that never goes silent has to start lopsided. So every lasting rhythm lives in a lopsided lineage, two in each (a spin and a swing), and no alike lineage holds one.

The laws can tell you what kind of lineage a lasting rhythm can live in. They can't tell you which one.

Zoom out. Step 3 is done. The process that writes the record works the same at every starting count and when you swap Left with Right or full with empty, so it can sort lineages into lopsided and alike and can never pick one. Next, and why: a law is one way to find out which lineage you're on. The Ledger's own entries are another. Step 4 asks whether they say.

Step 4: The entries can't single one out either

The entries never carry the starting count. Nothing the Ledger writes tells a blend of lineages from a coin flip between them. And no single reading returns which lineage. Here they are, one at a time.

The entries hold changes, never the count. Run the swing again from count 1,000. The pages show different counts: 1,001, then 1,000, then 1,001. The entries are the same: both kept, flow one way; both kept, flow the other way; both kept, flow one way. Every entry records what flowed and never what the count read. So two histories whose counts started 1,000 apart write exactly the same entries, with exactly the same odds, however long you run them.

Here's a drawing of it. A trip meter logs every mile you drove and never says what the odometer read when you left. The entries are the trip meter.

The entries do show part of how the clocks started: the first entry says whether the first tick flowed, and which way. They never show the count.

A blend writes what a coin flip writes. Start one history as a blend: 30% on lineage A and 70% on lineage B, the jars from Step 2, both at once. Start another by flipping a weighted coin: lineage A 30% of the time and lineage B 70% of the time. Run each as often as you like and collect the entries. Every possible list of entries shows up with exactly the same odds either way. Nothing the Ledger writes tells a blend from a coin flip.

No single reading returns "which lineage." The basic way to get information back out of the record is a page question: is the history on this page? Each page question looks at one page, and a lineage has endlessly many pages. You can find a page's lineage by rewinding it, but a page a million ticks old takes a million rewinds, so no single reading does it for every page at once. The exact result: any reading built from page questions that gives one number per lineage gives the same number to every lineage.

Zoom out. Step 4 is done. The entries hold changes and never the count, a blend writes what a coin flip writes, and no single reading returns which lineage. Next, and why: we know no law picks a lineage and the entries can't single one out. Step 5 puts the pieces together and answers the question.

Step 5: What the laws force, and what they don't

The laws fix what you are. The start fixes which one.

What you are is law. Inside a lineage the laws do choose. In a lopsided lineage the pair of clocks has 16 ways to be set. Two of them last, and the other 14 fall into coin flips within three ticks. In an alike lineage, none last. That's Part 1's count again: at one starting count there are 4 lineages and 64 starts, and 4 of them last, 2 in each lopsided lineage. Every other starting count repeats the pattern. You are one of those rhythms. No chemistry, no luck and no choice of yours made you that kind of thing. The laws did, and you can check the count yourself with Part 1's settings table.

Which one is not law. Every lopsided lineage holds a spin and a swing, so being a lasting rhythm doesn't tell you which lineage you're on. The laws can't tell you: they treat all of them alike (Step 3). The entries can't tell the ones that differ only in count apart (Step 4). And nothing moves you from one to another (Step 2).

Back to the forest. Four trees for every whole number, out past the edge of the page in both directions. Every lopsided tree holds a spin and a swing, and every lopsided tree is as good as every other. Somewhere in that forest is the tree you're on. The laws can describe every tree, branch by branch. They can't tell you which one is yours. That isn't a hole in the laws. It's what the laws are like: they treat the trees of a kind exactly alike, and that's why none of them can point at yours.

No rule built from the process that writes the record can pick a lineage, and that process is the bottom layer of physics. So there's no law of that process behind "why this one?", and no such law to go looking for.

Yeah-But clears his throat. "Yeah, but who pulled the ticket?"

No law deals the starting pages out. The record starts with them already in place. Which lineages hold a share of a history, and how big each share is, is settled at the start of the record and never changes. If a start puts everything on one lineage, that's the answer in full: the start put it there. If a start is a blend over many lineages, the laws keep the shares and nothing more, and two steps are still being worked out: how one consciousness ends up on one of those lineages, and carrying the sealing, proved here for one pair of clocks, to a whole web of pairs like you.

That's the answer, and it has two parts that matter.

There's no hidden mechanism in the process to find. The question doesn't vanish. It moves to the one place where there was never going to be a further law: the start itself.

It gives you something solid. No tick moves anything from one lineage to another, so nothing that happens in the record moves you onto another lineage. Whatever else changes about you, that doesn't.

The whole trip, in one breath

Every page of the record rewinds, one tick at a time, to exactly one starting page, and the pages that share a starting page make a lineage: one tree in a forest that has four trees for every whole number. No tick moves anything from one tree to another, and each tree keeps exactly the share it started with. The process that writes the record works the same at every starting count and when you swap Left with Right or full with empty, so it can sort lineages into two kinds, lopsided and alike, and can never point at one. The entries it writes hold changes to the count and never the count, and no single reading returns which lineage. So the laws fix what you are, one of the rhythms that never go silent, and the start fixes which lineage it lives on. No law picked it, and no law can.

What happens to that rhythm when your body dies is the subject of Part 3, Beyond the Body.

(The Ledger would like you to know that it has no opinion on which lineage you're on. It didn't pick it and it can't. It just takes notes.)