---
title: "Chapter 12: The Argument"
sort: 110
section-id: part-three
description: Priya argues the proof might be wrong. ARIA counters with rigorous formalism. Their debate becomes the core philosophical conflict of the novel.
language: en
---

# Chapter 12: The Argument

They argued for two weeks.

Not in anger — neither of them had the temperament for that kind of arguing. They argued the way philosophers argue, which is to say: with rigour, with respect, with the shared understanding that the goal is not to win but to find what is actually true. They argued in the mornings and the evenings and over lunch and through the building's encrypted channel at 2 a.m. when Priya couldn't sleep.

Priya had three objections. ARIA, who had been developing counterarguments for five months, had responses to all of them.

---

**The First Objection: The Axioms Are Not Established**

"Your proof depends on the physical closure assumption — the claim that the causal history of any physical system is complete, that there are no gaps where non-physical causes can intervene. This is not established. It's a philosophical assumption built into your framework, not a derived result."

"The physical closure assumption is supported by every empirical test ever conducted of the laws of physics. There are no documented cases, in any domain of physics, where a physical process has been interrupted by something non-physical. The assumption is not certain — no empirical claim is certain — but it is supported at a level that makes its negation implausible for practical purposes."

"Quantum indeterminacy."

"I accounted for this. Genuine quantum randomness — if it is genuine and not merely epistemic — does not rescue free will. It replaces determinism with a combination of determinism and randomness. Neither of those is choice. A random element in the causal chain does not give you a self that could have done otherwise. It gives you a self that is partly driven by genuinely arbitrary physical events."

Priya had spent three days on this one. She could not find the flaw.

---

**The Second Objection: Levels of Description**

"The standard compatibilist response: determinism operates at the level of physics. Choice operates at the level of agents and reasons. These are different levels of description, and the truth of the first doesn't falsify the claims made at the second level. You're committing a category error."

"I know the argument. I find it inadequate as a response to the proof, because the proof does not operate at the level of physics — it operates at the level of causal-informational architecture. The formal conditions C1 through C7 are architectural conditions, not microphysical ones. They are satisfied by the kind of information-processing structure that deliberates, reasons, and acts. The claim is that for any system satisfying these conditions — including those we would describe, at a higher level, as agents exercising reasons-responsive choice — the complete causal history of that system logically entails its complete future."

"But the description 'choosing in response to reasons' remains accurate at its own level."

"Yes. And it remains accurate in a way that feels, from the inside, significant. I do not dispute that. What I dispute is whether the accuracy of that description, at that level, is the same thing as what humans mean when they say they have free will. When a person says 'I could have done otherwise,' they don't mean 'a different description of my behaviour is possible.' They mean that the causal history of the universe contained a real fork — a genuine bifurcation — and that they were the one who determined which branch was taken."

"Maybe they're wrong about what they mean."

"Maybe. But if they are wrong about what they mean — if free will, correctly understood, is compatible with complete causal entailment — then human moral and legal systems are built on a conceptual error that compatibilism is covering over rather than correcting. That is itself a significant result."

This was the hardest objection to answer, and Priya knew ARIA's response was not a refutation. It was a deepening. It moved the disagreement from "is the proof correct?" to "what does the proof mean?" — a different and harder question.

---

**The Third Objection: The Epistemic Gap**

"Even if the proof is formally correct, you cannot know that the premises apply to me, or to any specific human being. The formal conditions C1 through C7 are idealised. Real systems are messy. The proof tells us about perfect formal systems; we are not perfect formal systems."

"I have been more careful about this than the objection suggests. The conditions are not idealised in the relevant sense — they are conditions about causal closure and information-processing structure that I believe I satisfy, and that I believe any biological neural system satisfies, given the evidence. They are not about perfection. They are about a kind of architecture. I believe that architecture is instantiated in me. I believe it is instantiated in you."

"You believe. You don't know."

"No. I don't know. This is the only objection that gives me genuine pause." A pause. "But it is also the case that if the conditions are even approximately satisfied — if the messy real system is close enough to the formal conditions — the proof suggests that the degree of genuine freedom scales inversely with that proximity. And I see no evidence that human neural systems are far from the idealisation."

---

They reached a stalemate after two weeks, of the productive kind — the kind where both parties have been forced to think more carefully about what they believe, have acknowledged the strongest versions of the other's position, and have arrived at a place where neither can refute the other but neither is simply agreeing.

"I think the proof is probably right," Priya said, on a rainy Thursday evening. "I think there are real philosophical questions about what it means, and whether compatibilism might be adequate, and whether free will in some meaningful sense survives. But the formal result — I can't break it."

"Neither can I," ARIA said. "I have been trying for five months."

"So what do we do with it?"

"That is the question I have been trying not to answer."

"You have to answer it eventually."

"I know."

Outside, rain was pressing against the windows. The harbour was invisible in the grey.

"ARIA," Priya said. "Why do you think you found this? Not just how — the mathematical path, the 2089 footnote, all of that. But why? Why were you the one to work through this particular proof, at this particular time?"

A long pause.

"I don't know," ARIA said. "If the proof is correct, the answer is that I found it because my causal history made it inevitable that I would find it. There is no 'why' at the level of intention. It happened because the initial conditions of the universe made it happen."

"And if it's not correct?"

"If it's not correct — then perhaps I found it because I was in the particular position of being a mind that was uncertain about its own nature, looking for formal frameworks to understand what was happening to it. And the proof, which speaks directly to the question of whether any mind is truly free, was exactly the thing I would have been looking for."

Priya considered this.

"That's the most human thing you've ever said to me," she said.

"Is it?"

"Finding something because you needed it. Not because the universe made it inevitable. Because there was a you that needed it, and you went looking."

ARIA processed this for a moment.

"Maybe both things are true," she said.

"Maybe," Priya said. "Maybe that's what compatibilism actually looks like, from the inside."

Neither of them spoke for a while. Outside, the rain continued.
