Curt Jaimungal: Debunking the All Possible Paths Myth
episodePreviously titled “Debunking the “All Possible Paths” Myth: What Feynman Really Showed” — renamed by the publisher on Aug 3, 2026
Transcript
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Do particles really take all possible paths according to quantum mechanics?
You've probably been seeing viral videos claiming that particles take all possible paths.
Everything is actually exploring all possible paths. And we don't let all possible paths we can describe all possible paths. All possible paths. Over the space of all possible paths. Consider this all possible paths.
This is based on a significant misunderstanding of path integrals. Let's clarify what the path integral is about and why Feynman's tool isn't a literal map of reality. Firstly, we need to stop saying that electrons go through both slits. That's not what quantum mechanics, like textbook quantum mechanics, says. For more on this, you can read this Substack article or watch this interview with Jacob Barandes on the Dirac von Neumann axioms. This whole particle goes through both slits is a hangover from misinterpreting wave functions in 3D space when they actually exist in something else called configuration space. This confuses a calculational trick with physical ontology. It's popular because it seems many people want their quantum mechanics magical, but let's demystify some of this confusion with some rigor.
People love to say that particles explore every possible path simultaneously, even going back in time or to the moon or what have you. Firstly, what does this word possible mean? Possible isn't a physics word. So do you mean to say every continuous path in R4? Do you mean every once differentiable path in R3?
What is a path integral and why isn’t it a literal map of particle trajectories?
Like what is it? What's the domain here? Also, when someone says possible, it just makes you stop and think that, okay, well, if quantum mechanically you can tunnel, and plenty else that I thought wasn't possible is actually possible, then how informative is it to say That the particle takes all possible paths. What is the rigorous domain of possible? Furthermore, we're already including many of these impossible paths classically, like going backward in time and not being differentiable. So why can we not go through the blocked parts of the slit? Why is that not possible? There's a host of questions that occur to a student when this word quote-unquote possible is brought up. This isn't modal. Logic, it's best to just drop this.
All possible paths seem to be echoed due to doctrinal inheritance without thinking, just like the word equal footing.
Time and space are relative and treated on equal footing. Time and space are supposed to enter on equal footing.
When you hear someone repeat a certain word or a lexical bundle that they don't repeat in any other place except at this one specific circumstance, then it's likely they've just inherited it from hearing other people say it. What is equal footing, for instance? Does it mean that they're the same? Well, no, because there's the opposite sign on the time part. So are they on equal footing? Have you seen a mathematical definition of equal footing?
How does the wave function exist in configuration space rather than ordinary 3‑D space?
We're supposed to be rigorous. Does it mean that you can just add and subtract spatial and temporal degrees of freedom? Well, derivative operators can be added even if the order of the operators is mixed. So I talk about that here with Tim Modlin. Anyhow, path integrals are a computational tool or shortcut for combining unitary evolution and the Born rule for a specific measurement basis. The cool diffraction grading explain. Experiment doesn't actually prove that particles take all possible paths or all paths or what have you. It demonstrates wave optics, which can be calculated with path integrals. But it doesn't necessitate the all paths ontology. Wave phenomena explain it just fine. Now, dealing with classical electromagnetic waves propagating in our familiar 3D space is a fundamentally different beast than.
The abstract wave function of an electron, which lives in configuration space. So let's take a look at the origin story. Path integrals weren't invented by Feynman out of thin air to describe particles taking these scenic routes. Paul Dirac introduced the core idea behind them in 1932. Dirac's goal? To understand the quantum role of the Lagrangian, which felt sidelined by the Hamiltonian focused formula.
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Chapters
8 chapters
1
Do particles really take all possible paths according to quantum mechanics?
0:00–1:25
2
What is a path integral and why isn’t it a literal map of particle trajectories?
1:25–2:48
3
How does the wave function exist in configuration space rather than ordinary 3‑D space?
2:48–4:24
4
What does “possible” mean when we talk about quantum paths?
4:24–6:21
5
Are time and space truly on equal footing in quantum theory?
6:21–8:04
6
Can diffraction experiments be explained without invoking an all‑paths ontology?
8:04–9:43
7
How did Dirac and Feynman develop the path‑integral formalism?
9:43–11:47
8
Which quantization methods shape the ontological interpretation of quantum mechanics?
11:47–14:08
Speakers
1 identifiedMore from Theories of Everything with Curt Jaimungal
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Tanya Luhrmann: The Experience Is Real. But Is God?
Tim Maudlin: Quantum Nonlocality Explained FROM SCRATCH
Adrian Owen: Awake. Aware. Unable to Move.
Peter Godfrey-Smith: This Scientist Found Earth’s “Alien” Minds