davidad has said, referring to the selection of books on the Library of EA:

I want to put in a strong bid to replace Parfit's On What Matters Volume One with Parfit's On What Matters Volume Three. Between volumes Two and Three, Parfit had many fruitful discourses with leading moral antirealists (Gibbard, Railton, Blackburn, etc), which are partially reproduced in Volume Three, where they really start to converge on some claims and get beyond their previous talking-past-each-other. It's truly amazing to read. Volume Three is self-contained and I think it should be considered as the best and final revision of Parfit's ethics.

Despite davidad's endorsement, there isn’t much other discussion of volume 3 of On What Matters on the EA Forum, or, for that matter, pretty much anywhere on the internet (leaving academic reviews aside). Richard Chappell's Moral truth without substance is the only other post I know of that discusses the book at length. Given davidad's glowing review, this seems worth fixing.

A taxonomy of metaethical views

Parfit begins his discussion with the following taxonomy of metaethical positions:

Adapted from page 56 of On What Matters, volume 3.

If, when looking at this, your first reaction was "Parfit [...]

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Outline:

(01:15) A taxonomy of metaethical views

(03:08) Are normative claims intended to state truths?

(04:58) Are there any normative truths?

(08:24) Are any of the normative truths irreducibly normative?

(13:01) Another Triple Theory

(16:20) Evolutionary debunking arguments

(19:04) The ontological status of Non-Realist Cognitivism

(23:59) Implications for the AI alignment discourse

(29:49) Climbing the mountain?

The original text contained 9 footnotes which were omitted from this narration.

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First published:
August 2nd, 2026

Source:
https://www.lesswrong.com/posts/jhvu4gXKETf2QqcR9/review-on-what-matters-volume-3

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Narrated by TYPE III AUDIO.

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Images from the article:

Adapted from page 56 of On What Matters, volume 3.

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“Review: On What Matters, volume 3” by Rauno Arike

LessWrong (30+ Karma)

“Review: On What Matters, volume 3” by Rauno Arike