C

Science begins with mystery. Arguably, the two greatest mysteries are the universe and awareness-the vast world out there and the powerful world within. Scientists attracted by one can be called to study the other, led by the thought that these mysteries are connected. Science writer George Musser's book Putting Ourselves Back in the Equation (方程) reviews their progress: Can physics unlock the mystery of awareness? Does awareness form the basis of fundamental physics?

The result is an ambitious but ultimately disappointing tour, filled with breathless encounters with well-known scientists. Representative of the cast is MIT's Max Tegmark, who tells Musser, "If you look at the problems that were still difficult to answer in fundamental physics, pretty much all of them trace back to awareness."

The book shows how physicists are contributing to understanding the mind, continuing a long

history of physicists exploring other fields. Musser integrates physics with neuroscience, economies, mathematics and more. Yet a key source of local knowledge is obviously absent-psychology. An early example: Musser rightly applauds physicists' contributions to artificial neural networks but is overly trustful of their implications, declaring that "ChatGPT" is already starting to demonstrate a generalized intelligence like that of humans. Interviewing more psychologists could have exposed the considerable gap remaining.

What about awareness itself? Why are some states associated with felt experience, such as the pain of a headache and the sight of a sunset, but others not? Musser's focus is integrated information theory (IIT). IIT begins with five self-evident principles of awareness: awareness exists, and it is structured, specific, unified, and definite. It then concludes assumptions concerning the causal structure of awareness systems, identifying awareness with integrated information. Finally, IIT offers a mathematical measure of this quantity: an equation for awareness.

However, despite its enthusiasts, IIT has significant problems. Its working basis is unfounded, and serious doubts surround its testability and definability. Of course, a theory of awareness must detail when, why, and to what degree we are aware of ourselves. Here, psychology's absence is most obvious. Over the last century, psychological research has revealed countless phenomena of awareness, from models that alter awareness to methods that stimulate unawareness; from extraordinary disorders of awareness to careful studies of metacognition (元认知).

Although questionable, such phenomena are the data that any scientific theory of awareness must account for. Yet these phenomena and ideas are almost nowhere in the book. Of course, psychology has not solved awareness, but one cannot hope to explain awareness without confronting these data.

Awareness is genuinely mysterious. So is fundamental physics. But hoping that physics can solve awareness while excluding other approaches is only a recipe for more mystery, not less.