I’ve stumbled upon a fascinating new paper recently titled “Consciousness as a State of Matter” (PDF link), authored by physicist Max Tegmark at Massachusetts Institute of Technology. I confess to have only read the first few pages of the paper, but the abstract (and introductory sections) intrigued me deeply:
We examine the hypothesis that consciousness can be understood as a state of matter, “perceptronium”, with distinctive information processing abilities. We explore five basic principles that may distinguish conscious matter from other physical systems such as solids, liquids and gases: the information, integration, independence, dynamics and utility principles. If such principles can identify conscious entities, then they can help solve the quantum factorization problem: why do conscious observers like us perceive the particular Hilbert space factorization corresponding to classical space (rather than Fourier space, say), and more generally, why do we perceive the world around us as a dynamic hierarchy of objects that are strongly integrated and relatively independent? Tensor factorization of matrices is found to play a central role, and our technical results include a theorem about Hamiltonian separability (defined using Hilbert-Schmidt superoperators) being maximized in the energy eigenbasis. Our approach generalizes Giulio Tononi’s integrated information framework for neural-network-based consciousness to arbitrary quantum systems, and we find interesting links to error-correcting codes, condensed matter criticality, and the Quantum Darwinism program, as well as an interesting connection between the emergence of consciousness and the emergence of time.
In the paper, Tegmark discusses the importance of characterizing consciousness as a state of matter like a solid, liquid, or gas:
What are the corresponding physical parameters that can help us identify conscious matter, and what are the key physical features that characterize it? If such parameters can be identied, understood and measured, this will help us identify (or at least rule out) consciousness from the outside”, without access to subjective introspection. This could be important for reaching consensus on many currently controversial topics, ranging from the future of articial intelligence to determining when an animal, fetus or unresponsive patient can feel pain. If would also be important for fundamental theoretical physics, by allowing us to identify conscious observers in our universe by using the equations of physics…
He then goes on to describe concepts of memory, Computronium (“the most general substance that can process information as a computer”), and Perceptronium (“the most general substance that feels subjectively self-aware”). A good summary of the paper is found in this post on Medium:
Tegmark uses this new way of thinking about consciousness as a lens through which to study one of the fundamental problems of quantum mechanics known as the quantum factorisation problem.
This arises because quantum mechanics describes the entire universe using three mathematical entities: an object known as a Hamiltonian that describes the total energy of the system; a density matrix that describes the relationship between all the quantum states in the system; and Schrodinger’s equation which describes how these things change with time.
The problem is that when the entire universe is described in these terms, there are an infinite number of mathematical solutions that include all possible quantum mechanical outcomes and many other even more exotic possibilities.
The entire paper, for those brave enough, would make for excellent bedside reading. Consciousness is one of those topics that I think a lot about (first having encountered it at Caltech via Kristof Koch’s book, The Quest for Consciousness).