Knowing Our Limits - Epistemology Without Bayes

Jan 28, 2026

A brisk tour of regulative versus descriptive approaches to finding truth. A critique of academic tone and the author’s fixation on “defeaters.” Discussion of the omission of Bayesian updating and its practical costs. A cautionary story about epistemic failure and polarization. Suggestions for alternative tools like Bayes, intellectual virtues, and collaborative inquiry.

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INSIGHT

Regulative Epistemology Emphasizes Finding Truth

Regulative epistemology focuses on how to find truth rather than defining it.
Ballantyne emphasizes high standards and favors reduced confidence over increased certainty.

ADVICE

Avoid Trespassing; Seek Collaboration

Avoid epistemic trespassing by not making confident claims outside your expertise.
Seek collaboration and get guides who provide both competence and criticism when crossing disciplines.

INSIGHT

Defeaters Versus Bayesian Updating

Ballantyne frames beliefs as defeated or undefeated and urges doxastic openness for controversial claims.
The host notes Bayes' theorem provides an alternative formal method for updating confidence that Ballantyne omits.

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I was promised useful stories to assist me in a quest for justified belief. Instead I got a lesson in the limits of expertise. Unfortunately it was the author's expertise that was limited.

Knowing Our Limits

By: Nathan Ballantyne Published: 2019 344 Pages

Briefly, what is this book about?

Regulative epistemology as opposed to descriptive epistemology. Put more simply, this is about how to find truth, as opposed to how to define truth. Though because the author recommends having very high standards, you may come away from the book thinking that there is no truth. That is not Ballantyne's intent, but most of his guidance revolves around less confidence rather than more confidence.

There is some good stuff about tolerance, and the utility of doubt. And while I take issue with some of what he says on the subject of expertise, he covers the subject exhaustively and thought-provokingly.

What authorial biases should I be aware of?

Ballantyne isn't just interested in epistemology. He doesn't dabble in it. He is epistemology, or rather an epistemologist. Accordingly, even though it's apparent that he's trying really, really hard to not make the book overly academic, it's still pretty academic. For example:

If an undefeated defeater for believing p were included in the evidence I don't have, then I (probably) would have heard of it by now. But I have not heard of it and the "silence" gives me reason to think that the unpossessed defeater is probably defeated.

He's a big fan of the word defeater, and various constructions involving the word. In the course of a few pages he uses the term "defeater-defeater" seventeen times.

Who should read this book?

Epistemological collapse is the major crisis of our time, so on some level it's probably useful to read everything you can get your hands on. (Which was my big reason for reading it.) But, as much as I crap on Yudkowsky's Rationality: From AI to Zombies I'd probably read his chapters on Bayes' Theorem before reading this.

I heard about the book on Jesse Singal's substack. He was much more bullish on it. So you might read that if you're interested or on the fence.

Specific thoughts: Lots of epistemic tools, Ballantyne really only covers one