The honesty this names
The book is built on one word — Turiya, the witness, the fourth — and puts it to nine traditions. But the word is not neutral: it comes from the Śaiva–Upaniṣadic stream, where the analysis of consciousness into states, and a fourth beneath them, is native. Carrying that map to the others asks a question that is sharply ours, and not always theirs. So two differences run through the book: what each tradition says the witness finally is, and — quieter — whether the witness is even the tradition's own question to begin with.
The stances — several, not two camps
Read across, not up. None of these is higher than another.
Advaita (which gave the word) · Kashmir Śaivism (which adds the further "beyond the fourth," turiyatita). The witness is named, central, analyzed as its own doctrine.
Yoga (puruṣa, the seer drawn clear of nature) · Dzogchen (rigpa, defined precisely so as not to be a Self). A witness-like standing reached through practice, not as a fourth state.
Zen — which asks whether there is any witness there to find at all.
Christian (not a state behind the others but Someone) · Daoist (not a witness but a way of moving with things) · Jewish & Sufi (cleave to an Infinite that stays other than the soul). The witness is not the thing they were looking for.
Two that resist quick filing
Sufism and Judaism are too easily filed as "relational, with no witness in them." They are not so simple.
Sufism holds a genuinely nondual current — Ibn ʿArabī's unity of being, in which only God's Being finally remains — set against the relational current that keeps the servant before the Beloved. The tradition argues the matter between two schools.
Judaism folds the same depth into one school: Chabad's "there is nothing besides God" dissolves the self's separate standing as thoroughly as any teaching in this book — and then, in the same breath, refuses to let the practitioner rest there, turning the nullification outward into the repair of the world.
The real spine
Not whether the self collapses, but what one is told to do with the collapse. The self's collapse is reached in these traditions too. What differs is the command that follows it: where one tradition lets the self be annihilated and remain so, another commands that the one who has been emptied be sent back, humbled, to mend what is broken — annihilation against repair.