The Dutch computer scientist turned philosopher of mind who argues consciousness is fundamental and matter is its appearance, the leading systematic voice of analytic idealism.
Documented
The dissociation argument
Kastrup's documented framework: the one consciousness, mind-at-large, undergoes dissociation the way a psyche forms alters in dissociative identity disorder, and each living being is such an alter, a whirlpool localizing the stream. The brain, on this view, is the extrinsic appearance of the dissociated process, which is why damaging it disrupts mind without producing it. Set out in Why Materialism Is Baloney (2014) and The Idea of the World (2019); debated publicly with Dennett's heirs and Graham Oppy.
Assessment: Documented as a rigorous, published position in philosophy of mind. Its strength is the hard problem's real failures; its weakness is that dissociation explains plurality by borrowing the least understood clinical phenomenon in psychiatry.
Stories
The dashboard with one driver
The folk synthesis pairs Kastrup with Donald Hoffman's interface theory: spacetime is the desktop, objects are icons, and shared biological hardware is why all users render the same world. The whirlpool metaphor does the emotional work, death as the eddy relaxing back into the ocean, and psychedelics as the user briefly seeing the desktop's source code.
Assessment: Hoffman's interface math and Kastrup's idealism are documented and mutually friendly. Neither entails the other; the folk fusion is tidier than either author's fine print.
Interesting claims
The demiurge, naturalized
The claim: analytic idealism is gnosticism with citations, mind-at-large as pleroma, dissociation as the fall into separate souls, the material world as the kenoma's UI. Kastrup himself resists the spiritual packaging; the esoteric reading adopts the architecture anyway.
Assessment: The structural rhyme with the gnostic system is real and Kastrup's secular framing is documented. The archive files the mapping, not the metaphysics.
Sources and further reading
Kastrup, Why Materialism Is Baloney, 2014
Kastrup, The Idea of the World, 2019
The dissociative identity disorder literature he draws on
Hoffman, The Case Against Reality, 2019, the interface parallel
Worth asking
If we are whirlpools in one ocean, was 'separate self' ever more than a pattern in the water?