Quantum Computing, Computational Complexity, and the Philosophical Limits of Prediction with Scott Aaronson

The conversation with Scott Aaronson, a leading expert in quantum computing and computational complexity, delves into the profound intersection of computer science, physics, and philosophy. Aaronson, known for his ability to communicate complex ideas, emphasizes that while philosophy tackles the "biggest questions," science and mathematics provide the tools to make tangible progress, often by reframing these grand riddles into "Q-prime" scientific or mathematical sub-questions. This approach allows for concrete answers that, while not fully resolving the original philosophical query, can fundamentally alter our understanding and discussion of it. He cites historical examples like Alan Turing's redefinition of "can machines think" into the empirically testable Turing Test, and Kurt Gödel's work on the limits of formal systems, demonstrating how precise, answerable questions can emerge from abstract philosophical debates. A central theme explored is the nature of free will and its relationship to predictability. Aaronson proposes a Q-prime for free will: "how well in principle consistently with the laws of physics could a person's behavior be predicted?" This shifts the debate from metaphysical definitions to empirical possibilities, drawing in concepts from neuroscience and quantum mechanics. The discussion touches upon the role of quantum randomness (e.g., in neural firing via thermal noise and chaotic amplification) as a potential limit to deterministic prediction. However, Aaronson notes that even probabilistic prediction might undermine the subjective experience of free will, suggesting that the "feeling of freedom" is deeply tied to the *unpredictability* of one's actions, not just their deterministic nature. A crucial nuance introduced is the destructive nature of quantum measurement. To predict a quantum system (like the brain) with extreme accuracy, one might fundamentally alter its state, thereby making perfect prediction impossible without destroying the subject. This raises questions about the feasibility of a hypothetical "prediction machine" that could foresee all future actions. Aaronson argues that the actual existence and demonstration of such a machine, or even a human-level AI, would profoundly transform the philosophical discourse around free will and consciousness, even if the "hard problem" of consciousness itself remains unanswered. The conversation highlights that progress in science can redefine the terms of philosophical engagement, making abstract questions more concrete and empirically grounded. Ultimately, the discussion underscores the idea that theoretical computer science, by exploring the ultimate limits of what can be known or calculated by physical entities, is in a sense studying "to what extent gods can be made manifest in the physical world." Quantum computing itself is presented as a new paradigm for computation, harnessing the non-intuitive principles of quantum mechanics—specifically, the use of complex "amplitudes" instead of probabilities to describe system states. This framework, while seemingly complex, offers a simpler way to understand quantum mechanics when viewed through the lens of information theory, emphasizing its potential to push the boundaries of what is computationally possible and, by extension, what we can understand about the universe and ourselves.

philosophy almost by definition is the subject that's concerned with the biggest questions that you could possibly ask

math and science are tools that we have for you know actually making progress and you know hopefully even you know changing our understanding of these philosophical questions sometimes even more than philosophy itself does

the only way to make progress on the big questions like the full of the philosophical questions we're talking about now is to pick off smaller sub questions ideally sub questions you can attack using math empirical observation or both

given an unanswerable philosophical riddle q replace it with a mirror leak in quotes scientific or mathematical question q prime which captures part of what people have wanted to know when they first asked q

instead of talking about is free will you know real where we get hung up on the meaning of you know what exactly do we mean by freedom... I suggested just asking the question how well in principle consistently with the laws of physics could a person's behavior be predicted

making a measurement on a quantum state is an inherently destructive operation

in a world where you know there were you know human-level AI is where we had been even overtaken by such a eyes the entire discussion of the hard problem of consciousness would have a different character

we are studying you know to what extent you know gods can be made manifest in the physical world

what does quantum mechanics say about the world you know the the physicists I think over the generations you know convinced people that that is an unbelievably complicated question and you know just give up on trying to understand it I can let you in not not being a physicist I can let you in on a secret which is that it becomes a lot simpler if you do what we do in quantum information theory and sort of take the physics out of it

fundamentally the world is described by you know these are let's say the possibilities for you know what a system could be doing are described using numbers called amplitudes