'I Am a Strange Loop' by Douglas Hofstadter

Hofstadter's explanation of how brain becomes mind dispenses with immaterial qualities and other kinds of philosophical hocus-pocus that bedevil efforts to solve the "mind-body problem." Trained as a physicist and a computer scientist but endowed with the soul of a philosopher, he posits that as our neurons fire in complex patterns that represent our perceptions, and as these representations (or symbols) swirl and dance in ever more complex ways, their interplay is strong enough and rich enough to produce awareness — that is, to become self-referential.

"Soul" is certainly not a term one expects from a materialist like Hofstadter. But in his lexicon, "soul" is interchangeable with "I," "self" or "consciousness" — just another name for the mind's strange loop. And because a strange loop is an aspect of a physical process, it — like anything physical — can be measured.