Letter to James Randi

Dear Mr. Randi:

I'm a graduate student in computer science at UC Berkeley and a longtime admirer of your work. In your January 26 commentary, you say of Stephen Hawking:

    "In my opinion, he gave a poor response to a question about astrology, poor because it allows the ignorant to fortify their fallacious opinions about what science really is. 'The reason most scientists don't believe in astrology,' Hawkins [sic] said, 'is because it is not consistent with our theories that have been tested by experiment.'"

By this criterion, you argue, people could equally well have rejected quantum mechanics when it was developed, since it too was inconsistent with prevailing theories of the time. You propose instead that astrology be rejected because of its failure in direct experiments. I've been mulling over your comment, since it seems to illustrate a conflict between two kinds of skepticism. Call them arrogant or smug, but I suspect Hawking is right that "most scientists" reject astrology and other pseudosciences without bothering to check the evidence for or against them. The question is, are they justified in doing this?

Let me offer an argument that they are justified. Astrology and other miraculous doctrines do not, in principle, contradict the idea of inviolable laws of physics. But if these doctrines were true, then the laws of physics would have to be much more complicated than we think they are. Instead of talking merely about quarks, neutrinos, and so on, the laws would have to refer to such high-level concepts as the alignment of the planets, "a good day to start new ventures," "a tall dark stranger," and so on.

This is admittedly vague, since what does "complicated" mean? A mystic might retort that, to her, quantum chromodynamics is more complicated than romantic love. But computer scientists have a way to make the argument a bit more precise. The Kolmogorov complexity of a piece of information is defined to be the length of the shortest computer program that outputs that information. Once we've agreed on a way to encode the universe as information, we can talk about the Kolmogorov complexity of the universe. We can then formulate a physical principle:

    The Low Kolmogorov Complexity (LKC) Principle: Under any reasonable encoding, the universe has low Kolmogorov complexity.

Intuitively, the LKC principle asserts that the laws of physics are simpleóprobably the same in all times and places, and almost certainly without special exemptions for life or human beings. The principle is, in my view, supported by the whole of science, which, through every major advance, has replaced complex or miraculous explanations by simpler ones. Based on the principle, I think that scientists are right to reject astrology without ever leaving their armchairs. Until, that is, astrologers can explain how their claims might be compatible with a low-Kolmogorov-complexity universe.

Steven Weinberg makes a similar argument in his Dreams of a Final Theory (1992), though he phrases it in terms of the explanatory framework of science rather than Kolmogorov complexity. Itís also interesting that, as detailed in Martin Gardner's Science: Good, Bad, and Bogus (1981), the reason Einstein gave for being skeptical of ESP was not its failure in experiments, but rather that its effects were claimed not to diminish with distance, in contrast to everything we know about long-range forces.

Of course, these sorts of arguments won't convince everyone. So, even though I found Hawking's remark perfectly agreeable, you're right that it might have been more politic for him to discuss the direct evidence against astrology. (Though Hawking is unlikely to be an expert on such evidence.) That's also why I think the work JREF does is importantóbecause when people lack even the rudiments of a scientific worldview, one can't persuade them via appeal to general principles, and the only hope lies in exposing the incompetence and self-deception that are the hallmarks of pseudoscience.

Best wishes,
Scott Aaronson


Scott: thank you for your welcome comments! Very good of you to share them with me. I don't believe in astrology because I'm a Sagittarius, and we're very hard to convince of anything!


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