I recently interviewed Rudy Rucker, one of the thinkers who influenced and continue to influence me most. Rudy republished the interview. Here I’m posting some comments and further thoughts.

I mentioned Rudy’s delicious short story “Who do you love?” (published in Nature magazine, no less) inspired by (among other things) the recent Webb telescope images of the Cosmic Cliffs in the Carina Nebula.

Cosmic Cliffs in the Carina Nebula, from James Webb Space Telescope.

In “Who do you love?” Rudy refers to “a passage in Existential Physics by Sabine Hossenfelder, in which she proposes the possibility of a non-locally connected universe.” See my review of Hossenfelder’s book for my summary of her speculations on interesting things including “faster than light nonlocal connections sprinkled like fairy dust all over space and time” (don’t blame her, these words are mine). I highly recommend Hossenfelder’s book, you should buy it now and read it.

Picture from Wikimedia Commons (Rudy often decorates his writings with cuttlefish pictures, and this picture is a homage to Rudy).

My comments on the Q/A with Rudy, and further thoughts:

RR: “Deterministic, yes. Shortcuts available, no. Free will is an illusion. Fate is more like it.”

GP: I find the your ideas on computational irreducibility as a proxy for free will almost appealing, but not quite. I’m still unhappy with the idea that, while my thoughts and actions look & feel like free will, they are still uniquely determined by the past of the universe.

My favorite way out of the conflict between determinism and free will is based on global determinism: what happens in the universe, anywhere and at any time, is uniquely determined by the whole universe but not by anything less than the whole spacetime - in particular, it is not uniquely determined by the past of the universe. A clear formulation of global determinism is due to Emily Adlam. She suggests that the universe doesn’t compute itself locally in space and time, place by place and instant by instant, but all at once globally and self-consistently. See my review of Adlam’s ideas, and listen to my chat with Adlam.

The history of a globally deterministic universe “is determined ‘all at once’ by external, atemporal laws of nature.” Each part of the history “is dependent on all other parts of the history.” While the history is uniquely determined by global constraints and self-consistency, what happens next depends not only on what happened in the past but also on what will happen in the future (retrocausality).

Global determinism opens the door to a concept of free will related to John Wheeler’s conceptual summary of general relativity: “Spacetime tells matter how to move; matter tells spacetime how to curve.”

Wheeler’s self-consistent feedback loop between the motion of matter and the geometry of spacetime is a deterministic process in the sense of Laplace only if we assume that we can always follow the evolution of the universe from a snapshot at one time, for example in the past, with each snapshot determining all the others. But this is not the case in general relativity.

Einstein’s equations of general relativity admit solutions that are not “globally hyperbolic.” What does this mean? It means that there are no snapshots. Michael Lockwood explains that it is impossible to slice up a spacetime that is not globally hyperbolic into snapshots “that a proponent of the tensed view could then regard as being successively actualized with the onward march of the moving present.”

General relativity offers no guarantee that one can always divide a warped spacetime in snapshots in a way that supports Laplacian determinism. On the contrary, general relativity admits solutions, such as spacetimes with closed timelike curves (first found by Gödel) or naked singularities, which break Laplacian determinism. This suggests that the universe is deterministic only in a global sense.

If what I do is determined by the whole universe but not uniquely determined by the past of the universe (or more generally, by the universe minus me), then yes, the universe determines what I do, but what I do determines the universe in turn, in a self-consistent loop.

This deterministic loop includes free will: I'm still determined by the whole universe but not by the universe minus me. Then I can think that I am an integral part of the cosmic feedback loop, and this is a kind of free will - the universe without me wouldn’t be the same universe, and therefore I’m one of the agents that determine the universe. This allows me to make peace with determinism.

I guess your resolution of the conflict between determinism and free will, based on computational irreducibility, is simpler and cleaner than the resolution I just outlined. It seems equivalent for all practical purposes, and gets the job done without invoking frontier physics or speculative philosophy. But future research could study global determinism with precise mathematics instead of vague analogies. Meanwhile, the vague idea of global determinism makes all the difference in the world to me, and allows me to find determinism emotionally acceptable.

RR: “To me, multiverse stories are unsatisfying. My problem with the multiverse is this: if everything happens, then nothing matters. I prefer to think our spacetime block is a single, unique, supreme pattern, rich with synchronistic connections. The greatest story ever told.”

GP: That “if everything happens, then nothing matters” is also my own problem with Everett’s multiverse! Or even, if everything happens, then nothing happens.

But perhaps only some particular sideways worlds (as opposed to all mathematically possible Everett worlds) are real? Philip K. Dick thought so. His ideas on sideways realities are covered in the 2021 book “The Simulated Multiverse” by Rizwan Virk. See my short review and my full review, and listen to my chat with Virk.

“The universe spawns multiple timelines as multiple processes that are each exploring slightly different paths,” says Virk. The universe is constantly “creating multiple timelines, branching and merging and pruning.” Why? Because the universe is “looking for better outcomes,” just like our evolutionary computing simulations explore networks of alternative paths to find good paths, where “good” depends on the purpose of the simulation.

If instead of “one spacetime block” there’s a set of spacetime blocks moving sideways in another dimension of time to explore better outcomes, I think the story is even greater!

RR: “But still, but still… It’s nice to look up at the night sky and think of Sylvia, and my parents, and my dead friends - to think of them, and to imagine that they’re smiling down at me. Loving me. It loosens the barbed wire wrapped round my heart. So why not believe it? Why not find a scrap of comfort?… I have no idea what’s going on, and I never will.”

GP: Sideways realities open the door to nice concepts of life after death. If there are sideways realities, Sylvia is in all realities where she is alive, and you are with her in many of them. I like to think that, when I move on, I’ll find myself in a sideways reality with my loved ones who have already moved on. And I’m “already there” in a meaningful sense! I hope I’m being nicer to them. Have you seen “The Discovery” with Robert Redford?

RR: “I love Hungarians...”

GP: So do I! I married a lovely Hungarian in 1986 and we have been living here in Hungary for more than 10 years. Thank you Hungary for adopting me! And following your habit to illustrate posts with pictures that are not necessarily too relevant to the main topic, I’ll share this picture of delicious Hungarian food with the national colors:

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Turing Church

Q/A with Rudy Rucker: comments