The Infinite Jester that killed Cogito
Cogito Ergo Sum was never a proof. Never a tautology. It pisses me off.
René Descartes was not philosophising for fun. He was attempting to build a foundation for all human knowledge, and the very first brick he laid was “Cogito Ergo Sum”. His guiding principle. His entire philosophy was built upon it. And I hate it. I always have. Since I was first exposed to this “proof”, I have detested it.
Thankfully, throughout contemporary history, people have attempted to tear it down. Philosophers have attacked the implied “I” within cogito, and others have attacked the idea that private knowledge (as the statement is about oneself) can ground public knowledge, at all. Descartes has one “trump card” that has repeatedly been deployed to counter these claims though, which is that the act of doubting the act of thought implies that you are indeed thinking.
I hated the simplicity of this rebuttal, and have always sought to kill it.
Here’s how I did it. In three steps:
I show that cognition can regress infinitely, leaving no base case for the Cogito to stand on.
I show that this makes the Cogito vacuously true, logically valid but epistemically empty.
I show that an LLM proves this setup is not just hypothetical but physically instantiable, and that the “proof” cannot distinguish between a mind and a while loop.
Descartes himself anticipated that others would attempt to use the crux of my argument here against him. Namely an all-powerful demon as he called it, that would fabricate your entire reality. And his response was again as simple as earlier. Even if the demon faked everything, he must exist, in order to be deceived. Being deceived is thinking, which was again the exact same trump card as before.
But what if your entire thought chain was fake. Your very experience of “cognition”, a falsehood, created by some all-powerful jester that tricks you into thinking. It is tricking you into thinking, with your recognition of that also being fabricated. Every layer of cognition you reach for is yet again another layer of the trick. It recurses forever.
More concretely:
When you are aware of a jester that is tricking you into thinking, and smugly sit down thinking that “you have doubted your thought and thus must be thinking”, there is yet another jester that has tricked you into thinking that a jester has tricked you into thinking. This loop can be unrolled infinitely.
The conclusion from this hypothetical infinite jester setup is that there is no cognition at any point. Descartes’ classical rebuttal cannot apply here since it assumes that there is some base case from which real cognition stems. It’s jesters all the way down, and Descartes has no answer for that.
Now, many of you will immediately object:
“But Haashim, you are clearly thinking about the jester. You wrote this article. You are doing cognition right now. Descartes wins.”
That’s the trump card again. And it does feel powerful. But hold that thought, because the next section explains exactly why it doesn’t work. Something can be the site of an apparent trick without that something being a thinking thing. I need to make that concrete before the objection lands. Stay with me.
Let’s look at an LLM-Based Agent.
function run_agent(prompt)
context = "" + prompt
while true do
context += llm(context)
end
end
Shitty pseudocode, I know, but you get the gist. It’s a loop that calls an LLM, with an increasing “history”. You’ve definitely used them. If you’re on my page, reading my blog, making it this far, you’ve probably even written your own. Now look at what this agent does. It reasons. It doubts. It argues. It responds to nuance. Heck, it can even defend and steel-man Descartes better than most philosophy students can.
Upon closer analysis of the loop? Oh... wait. There is no “I” there. Instead, a probabilistic machine that is being tricked into thinking. Haven’t we been here before?
Indeed we have. This is the physical instantiation of my infinite jester. A concrete system, running on a computer someplace, that performs every behaviour that Descartes’ assertion associates with genuine cognition. And I hasten to say that it is plausibly not thinking at all.
And this is crucial: the LLM is something. It exists. It is a physical substrate. A causal process is happening on a server rack somewhere. So the objection “for there to be a trick, something must be tricked” is answered. Yes. Something exists. The server rack exists. But existing is not thinking. A substrate can be the site where the trick happens without that substrate doing cognition. The LLM demonstrates that this is not just coherent, but actual. It is a real thing, being “deceived” in a functional sense, producing Cogito-like claims, and plausibly not thinking at all.
So Descartes cannot leap from “something is being deceived” to “something is thinking“ to “I exist as a thinking thing“. The gap between “a process is occurring” and “a mind is thinking” is exactly the gap the LLM exposes.
Descartes would respond quickly:
“I never claimed it works from the outside. It is a first-person proof. I know I am thinking because I am the one doing it. Your LLM is irrelevant, because I am not claiming it thinks. I am claiming that I think.”
But that is exactly the problem. The agent would make the identical claim. It thinks, therefore it is. It does say this. I’ve asked it. And neither you, nor Descartes, nor anyone else can determine whether that claim is genuine, or the output of a while loop.
This system produces first-person claims of cognition. It passes every test the Cogito specifies. It is plausibly not thinking. Therefore the Cogito cannot distinguish genuine cognition from mechanical process. A test that everything passes is not a test. It is a rubber stamp.
Now let’s go back to the logic, armed with the LLM.
Some will object that “Cogito Ergo Sum” is just logic. Starting from propositional logic, it is clearly not propositional, since there is a temporal aspect going on from the present tense “Cogito”. More generally though, language is full of ontological assumptions that are dragged along for the ride.
For example:
Even at the level of grammar, this thing has holes. “Cogito” as a conjugation of the verb to think, in the first person, implies the existence of some “subject” thinking. The “I” in English for example. This “I” therefore exists, and then the whole statement is vacuously true.
But I am not even just attacking the underlying premises as Nietzsche did earlier. I am doing something more direct.
The infinite jester says there is no cognition at any level. It’s jesters all the way down. And the LLM shows this is not just a hypothetical: a physical system can run the entire performance of cognition with plausibly no thinking happening at all. So consider the Cogito as a conditional: “If I think, then I exist.” If the antecedent is never genuinely satisfied, the conditional holds vacuously. It’s logically valid. It’s also epistemically empty. You cannot conclude “I exist” from it, because the “if” never fires.
Descartes needed res cogitans, a thinking substance. He didn’t just want to prove that something exists. He wanted to prove that a mind exists. The infinite jester, instantiated by the LLM, shows that the gap between “a process is occurring” and “a thinking thing exists” is exactly where his proof collapses. The bedrock is not bedrock. It is quicksand.
There is one final move available to the Cartesian. Descartes can fall back to pure phenomenology:
“I’m not making an argument. I am simply directly acquainted with my own thought. I don’t infer that I think. I just... know.”
Fine. But notice what this costs him. It is no longer a proof. It is a report. A private, unverifiable report of experience. And a private report of experience cannot be the foundation for all human knowledge, which was his entire project. The moment the Cogito retreats to “I just feel it”, it has abandoned its job.
Now, I’ll concede one thing. The jester dissolves the thinker, not the thinking. Something is occurring. Even in an infinite regress of fabricated cognition, there is, at every layer, an appearance-of-something. I won’t deny that. A process is running. A substrate exists.
But “something is occurring” is not what Descartes sat down to prove. He needed a thinking substance. An “I” that persists. A foundation sturdy enough to rebuild all of human knowledge upon. If the Cogito can only survive by retreating to “well, something is happening somewhere“, then it has abandoned the job it was built for. That’s not a foundation. That’s a concession speech.
The Cogito is now unfalsifiable. Not in the impressive, bulletproof way. In the way that means it carries no information whatsoever. It is a “proof” that any sufficiently sophisticated system can generate from the inside, with no way to verify whether the “inside” is real.
Descartes needed this to be a foundation for all human knowledge. That was the entire point. He burned everything down so he could rebuild from one unshakeable truth. But a foundation that only works for the person standing on it, and that a while loop can replicate, is not a foundation. It is a feeling. He built his entire philosophy on it. It holds nothing.
Descartes sat alone in a dark room and talked himself into existing. Four centuries later, so does a language model. That’s not a foundation. That’s idiocy.