ClaimsEliezer Yudkowsky

“that ignorance is a mental rather than physical property.”

Eliezer Yudkowsky, posting on X 26 December 2020 Post by @ESYudkowsky on X, 2020-12-26 (X)

Factual Science and research methods

E. T. Jaynes said many times that probability is ignorance and that ignorance is a mental rather than physical property, and Yudkowsky repeated this often.

Mostly true True in substance, wrong in a detail.

Factual: Statements about the present or the past, checked against the record: did they hold up?

The second judge would not resolve this claim; the verdict shown is the first judge's.

What would count as true or false

True: Jaynes's writings (for example Probability Theory: The Logic of Science, or 'Probability in Quantum Theory') repeatedly state that probability expresses a state of knowledge or ignorance and is not a physical property, criticising the 'mind projection fallacy'. In addition, Yudkowsky's writings repeatedly restate this idea before 2020-12-26 (for example LessWrong posts such as 'Probability is in the Mind' and 'Mind Projection Fallacy'). Mostly true: both parts hold in substance, but Jaynes's wording differs (he speaks of 'states of knowledge' rather than literally 'ignorance is mental'), or he said it only a few times rather than 'many times'. Mixed: one part holds and the other does not. Mostly false: Jaynes held a related but materially different view, or he stated it only once. False: Jaynes did not hold that probability reflects a state of knowledge rather than a physical property, or neither Jaynes nor Yudkowsky repeatedly stated it.

Set before the research began.

Evidence (4)

  1. E1 Probability Theory as Logic E. T. Jaynes (Washington University), in P. F. Fougere (ed.), Maximum Entropy and Bayesian Methods, Kluwer · 1990

    “At the 1988 workshop we called attention to the "Mind Projection Fallacy" which is present in all fields that use probability.”

  2. E2 Probability Theory as Logic E. T. Jaynes (Washington University), in P. F. Fougere (ed.), Maximum Entropy and Bayesian Methods, Kluwer · 1990

    “Probability theory is far more useful if we recognize that probabilities express fundamentally logical inferences pertaining to individual cases.”

  3. E3 Mind Projection Fallacy — LessWrong LessWrong · 11 March 2008 Own record

    “E. T. Jaynes used the term Mind Projection Fallacy to denote the error of projecting your own mind's properties into the external world.”

  4. E4 Rationality: A-Z — LessWrong LessWrong · 12 March 2008 Own record

    “Jaynes was of the opinion that probabilities were in the mind, not in the environment—that probabilities express ignorance, states of partial information; and if I am ignorant of a phenomenon, that is a fact about my state of mind, not a fact about the phenomenon.”

Reasoning

In his 1990 paper (E1, E2), Jaynes says probabilities express logical inferences. He also says he had raised the 'Mind Projection Fallacy' at the 1988 workshop, so he made the point on more than one occasion. Yudkowsky's 2008 LessWrong posts (E3, E4) restate the idea directly: they say probabilities express ignorance and that ignorance is a fact about one's mind, not about the phenomenon. Both parts hold in substance. However, the Jaynes passages in evidence talk about logical inference and the mind projection fallacy rather than literally saying 'ignorance is mental', and they don't show that he said it 'many times'.

Cite this claim

Eliezer Yudkowsky, “E. T. Jaynes said many times that probability is ignorance and that ignorance is a mental rather than physical property, and Yudkowsky repeated this often.” (said 26 December 2020). Verdict: mostly true. Reliability API, claim c_4fb704d95885, method 0.1.0+c876030c, dataset release v1.1.2. https://epistacklabs.com/claims/c_4fb704d95885

This claim is in dataset release v1.1.2, with the same verdict.

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More factual claims by Eliezer Yudkowsky

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    “And that in turn provided a lot of indirect support for the atomic theory.”

    Conservation of mass provided a lot of indirect support for atomic theory.

  2. Mostly true Factual September 2025
    “The conservation of mass was one of the first hints that things were being rearranged rather than created or destroyed.”

    The conservation of mass was one of the first hints that things are rearranged rather than created or destroyed.

  3. Resolved true Factual September 2025
    “The way that if you burn something inside a sealed glass vessel, it didn't change weight.”

    Burning a substance inside a sealed glass vessel does not change the total weight.

  4. Mixed Factual 2008
    “General intelligence is a between-species difference, a complex adaptation, and a human universal found in all known cultures.”

    General intelligence is a between-species difference, a complex adaptation, and a human universal found in all known cultures.

  5. Mixed Factual 2008
    “This is the edited volume that helped establish the field, written with the outside academic reader firmly in mind.”

    The Kahneman, Slovic and Tversky edited volume helped establish the heuristics and biases field and was written with outside academic readers in mind.

All of them

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