What do you think?
Rate this book
The Ghost in the Quantum Turing Machine
In honor of Alan Turing's hundredth birthday, I unwisely set out some thoughts about one of Turing's obsessions throughout his life, the question of physics and free will. I focus relatively narrowly on a notion that I call "Knightian freedom": a certain kind of in-principle physical unpredictability that goes beyond probabilistic unpredictability. Other, more metaphysical aspects of free will I regard as possibly outside the scope of science.
I examine a viewpoint, suggested independently by Carl Hoefer, Cristi Stoica, and even Turing himself, that tries to find scope for "freedom" in the universe's boundary conditions rather than in the dynamical laws. Taking this viewpoint seriously leads to many interesting conceptual problems. I investigate how far one can go toward solving those problems, and along the way, encounter (among other things) the No-Cloning Theorem, the measurement problem, decoherence, chaos, the arrow of time, the holographic principle, Newcomb's paradox, Boltzmann brains, algorithmic information theory, and the Common Prior Assumption. I also compare the viewpoint explored here to the more radical speculations of Roger Penrose.
The result of all this is an unusual perspective on time, quantum mechanics, and causation, of which I myself remain skeptical, but which has several appealing features. Among other things, it suggests interesting empirical questions in neuroscience, physics, and cosmology; and takes a millennia-old philosophical debate into some underexplored territory.
I examine a viewpoint, suggested independently by Carl Hoefer, Cristi Stoica, and even Turing himself, that tries to find scope for "freedom" in the universe's boundary conditions rather than in the dynamical laws. Taking this viewpoint seriously leads to many interesting conceptual problems. I investigate how far one can go toward solving those problems, and along the way, encounter (among other things) the No-Cloning Theorem, the measurement problem, decoherence, chaos, the arrow of time, the holographic principle, Newcomb's paradox, Boltzmann brains, algorithmic information theory, and the Common Prior Assumption. I also compare the viewpoint explored here to the more radical speculations of Roger Penrose.
The result of all this is an unusual perspective on time, quantum mechanics, and causation, of which I myself remain skeptical, but which has several appealing features. Among other things, it suggests interesting empirical questions in neuroscience, physics, and cosmology; and takes a millennia-old philosophical debate into some underexplored territory.
- GenresMetaphysicsPhilosophy
85 pages, Unknown Binding
Published June 7, 2013
50 people want to read
Ratings & Reviews
Friends & Following
Create a free account to discover what your friends think of this book!
Community Reviews
Displaying 1 - 2 of 2 reviews
February 4, 2023
Even though I do not subscribe to his proposal, I have to confess this was one of the intellectually densest essays I've read, if not the densest.
The essay is centered on the idea of freebits, which is an Alan Turing influence from the "Computing Machinery and Intelligence" paper. In it, Turing stated that “It is probably wise to include a random element in a learning machine”, as he believed that in order to create truly intelligent machines it is necessary to include some element of randomness (or freedom) in their operation, rather than having them solely follow a predetermined set of rules.
Scott tries to find scope for "freedom" in the Universe's boundary conditions rather than its dynamical laws. Boundary conditions are called such because they refer to the parameters that define a system's boundaries, or limits. These can include things like initial positions and velocities of particles or fields, as well as other physical properties which determine how these systems will evolve over time. By looking at changes in boundary conditions rather than dynamical laws (the rules governing the evolution), it is possible to find scope for unpredictability within deterministic physics - something which could provide room for free-will like behavior. For example, a tool for studying boundary conditions is the phase space, which display the states of a system that are reachable from the initial conditions and that are consistent with the constraints of the system.
Scott asked himself:
And in answering this question, the reader is reluctantly absorbed in a maze of concepts; from computer science to physics and everything in between.
The essay is centered on the idea of freebits, which is an Alan Turing influence from the "Computing Machinery and Intelligence" paper. In it, Turing stated that “It is probably wise to include a random element in a learning machine”, as he believed that in order to create truly intelligent machines it is necessary to include some element of randomness (or freedom) in their operation, rather than having them solely follow a predetermined set of rules.
Scott tries to find scope for "freedom" in the Universe's boundary conditions rather than its dynamical laws. Boundary conditions are called such because they refer to the parameters that define a system's boundaries, or limits. These can include things like initial positions and velocities of particles or fields, as well as other physical properties which determine how these systems will evolve over time. By looking at changes in boundary conditions rather than dynamical laws (the rules governing the evolution), it is possible to find scope for unpredictability within deterministic physics - something which could provide room for free-will like behavior. For example, a tool for studying boundary conditions is the phase space, which display the states of a system that are reachable from the initial conditions and that are consistent with the constraints of the system.
Scott asked himself:
Could there exist a machine, consistent with the laws of physics, that “non–invasively cloned” all the information in a particular human brain that was relevant to behavior, so that the human could emerge from the machine unharmed, but would thereafter be fully probabilistically predictable given his or her future sense-inputs, in much the same sense that a radioactive atom is probabilistically predictable?
And in answering this question, the reader is reluctantly absorbed in a maze of concepts; from computer science to physics and everything in between.
July 30, 2024
Absolutely fascinating. A bit dense, but I'm already cheating counting this on goodreads so I suppose I can't complain. I found it an interesting formalism of the role of randomness in breaking the deterministic chain, via the 'freebits' that Aaronson posits, but I think things get muddled when attempting to form a positive proof of free will and a falsifiable picture. Very cool way to tie in quantum mechanics to philosophy though, and original and forward thinking in a way that is lacking in contemporary science. A striking vision of the future! Thank you Danny for the recommendation.
Displaying 1 - 2 of 2 reviews