This post is somewhat niche, and I will sometimes not give context or link relevant background.

There's a big debate that has played out in slow motion on LessWrong over the past two decades, between two broad ways of putting a measure over all possible realities (often specifically Tegmark IV):

Some “objective” prior (a “reality fluid”), usually a simplicity prior: This is the position taken by Max Tegmark, Jürgen Schmidhuber and UDASSA.
A “caring measure”, where we say that our preferences determine our probabilities and maybe even what counts as “existing”. For example, Wei Dai here, Paul Christiano here and Scott Garrabrant.

These both have significant drawbacks:

A simplicity prior seems to imply some very counterintuitive things, like caring about people more the easier we can find them in the universe (and even weirder things, see David Matolcsi here and Joe Carlsmith here), and is partially dependent on an arbitrary choice of implementation (e.g. which Universal Turing Machine to use in UDASSA).
A caring measure just seems a bit unmotivated - intuitively, our probabilities (or existence itself) shouldn’t entirely depend on our preferences. Ideally, we’d like something better.

Unfortunately, there are infinite possible worlds and every event [...]

The original text contained 5 footnotes which were omitted from this narration.

---

First published:
August 23rd, 2026

Source:
https://www.lesswrong.com/posts/m5XNyahxizKfboEnk/psa-there-s-a-third-option-in-the-measure-problem

---

Narrated by TYPE III AUDIO.

“PSA: There’s a third option in the “measure problem”” by Elias Schmied

LessWrong (30+ Karma)

“PSA: There’s a third option in the “measure problem”” by Elias Schmied