6 ideas
In The Assayer (1623), Galileo argued that colors, tastes, and smells do not exist in objects but only in the perceiving soul, while matter itself has only mathematical properties like size, shape, and motion. This move made a purely mathematical physics possible. It worked by setting consciousness aside, and it left the mind as the one thing the new science could not describe.
Physics characterizes entities purely by their causal and mathematical structure, meaning how mass or charge disposes things to behave. It is silent on what those entities intrinsically are. That leaves a gap in our picture of reality, where the underlying nature of matter is unknown rather than known to be non-experiential.
Following Bertrand Russell and Arthur Eddington, consciousness is proposed as the intrinsic nature of matter. Physics captures that nature from the outside, as dispositions and structure, while experience is what it is from the inside. On this view the brain's consciousness is not an anomaly added to physical matter. It is the one place where we directly know matter's intrinsic nature.
Goff sets out the knowledge argument, in which Mary, a scientist who knows every physical fact about color but has never seen red, learns something new on first seeing it. He pairs it with the conceivability of zombies. Together these show that a purely quantitative, third-person vocabulary leaves out qualitative experience. Materialism fails because its descriptive toolkit was built by excluding qualities in the first place.
If fundamental particles have extremely simple forms of experience, panpsychism must explain how many tiny subjects combine into one unified human subject. It must also explain why a rock does not form a unified mind. This is the theory's central open challenge. Goff treats it as a research program to be worked on, possibly through cosmopsychism, which starts from a conscious universe and explains minds as parts of it.
Materialism must deny or explain away something known with certainty, our own experience. Dualism adds a separate mental substance that interacts mysteriously with the physical. Panpsychism posits a single kind of stuff whose intrinsic nature is experiential, so theoretical parsimony favors it once both known data points are counted: the structure described by physics and the consciousness known from within.