About Rationally Speaking

Rationally Speaking is a blog maintained by Prof. Massimo Pigliucci, a philosopher at the City University of New York. The blog reflects the Enlightenment figure Marquis de Condorcet's idea of what a public intellectual (yes, we know, that's such a bad word) ought to be: someone who devotes himself to "the tracking down of prejudices in the hiding places where priests, the schools, the government, and all long-established institutions had gathered and protected them." You're welcome. Please notice that the contents of this blog can be reprinted under the standard Creative Commons license.

Monday, November 07, 2011

New Rationally Speaking podcast: SETI

Is the search for extraterrestrial intelligence, or SETI, solid science, pseudoscience, or something else, as Massimo argues in his book "Nonsense on Stilts"?

What are the theoretical foundations and empirical evidence that justify a multi-decade research program, and what are its chances of succeeding? Have we learned anything thanks to SETI?

Also, if the universe is infinite, what problems does this pose for utilitarian ethics?


  1. You deny the impossibility of proving a negative by pointing out that it is possible to find out whether or not there is something in your pocket. I think you should take this to a more fundamental level and ask how we can know what we don't know. I wonder if there is a better option for uncertainty robustness than SETI and if not, why that would not be the best argument to keep it in the air so to speak?

  2. This comes up fairly regularly and it always bugs me. Is SETI practical? What justifies the cost? Is it real science? Blah blah blah...

    Practicality is great. We get new and improved gizmos every year. Medicine for profit gets us a never ending stream of expensive drugs that treat symptoms but never actually cure anything. And let's not forget weapons! How would we ever get along without better ways to blow shit up?

    SETI, on the other hand, costs practically nothing when compared to those "practical" sciences, employs some very very smart people in a noble thought experiment, and could lead to the greatest discovery in the history of history. Where is the down side? A tiny (very tiny) sliver of the Pentagon's annual budget could fund SETI for decades.

    Sure, space is really big and it might just be that the distances between intelligent species are just too vast to ever make contact...but what if?

    Isn't is worth a few bucks just in case?

  3. Ron,

    to be clear, I argue that *some* negatives *can* be proven with the money-in-the-pocket example. Not sure what you mean by uncertainty robustness, care to elaborate?


    part of the discussion was about whether SETI even counts as science, about which there is much reasonable debate. And it doesn't cost "a few bucks," we are talking about tens of millions (possibly hundreds) over an open-ended period of time. Surely we could do other things (other than weapons) with some of that money...

  4. Isn't "you can't prove a negative" itself a negative and, therefore, unable to be proven?

    Looking forward to listening to this episode after work tonight.

  5. I wonder where this "you can't prove a negative" nonsense comes from, anyway? I mean, most anti-epistemology is pretty transparent but this just seems odd...

    I was surprised, Massimo, to hear that you didn't think the discovery of extremophiles moved the probabilities very much or at all. It seems to me that if before we thought life needed a very narrow range of conditions, and now we know that that range isn't quite as narrow as we thought, that increases our credence in the feasibility of extraterrestrial life. Of course, it's only one factor in this long diminishing product of probabilities, but still...

  6. Ian,

    well, I guessed I'm not as impressed by extremophiles as some of my colleagues. Fascinating stuff, but they really expand the range for life by a fraction, and they were not quite as unexpected as some people seem to think. Besides, I think some of the other factors in the Drake equation are more crucial, and more likely to veer negative.

  7. Ian,

    Re: 'I wonder where this "you can't prove a negative" nonsense comes from, anyway?'

    If S asserts p, there are unicorns, S asserts a particular (aka existential) statement:

    (1) (∃x)(Ux)

    In words, there exists at least one x such that x is a unicorn.

    Now, the negation of (∃x)(Ux) is a universal statement:

    (2) ¬(∃x)(Ux) = (∀x)¬(Ux)

    In words, (∀x)¬(Ux) reads: It is not the case that there is at least one x such that x is a unicorn, which is to say, for every x it is not the case that x is a unicorn.

    Establishing the truth of (1) is easy: We observe a unicorn. However, establishing the truth of (2) is not easy. In fact, it is impossible. [There are particular exceptions: If one limits the domain of discourse, one can prove a universal statement true: (∀x)¬(Ux ∧ Rx). In words, for every x it is not the case that there is a unicorn and it is in this room. The contents of one's pockets is a similar limitation of domains.]

    It is in this sense that one cannot prove a negative and it certainly is not nonsense.

  8. Massimo,

    I am inclined to agree with your view on SETI. Let us grant that there is life of some sort (as I am convinced there probably is) and that there is even intelligent life (I am less confident in this). Given how large the universe is, it seems very unlikely that we should detect any evidence of alien intelligence.

  9. I don't understand Massimo's conclusion that nothing has really changed that would increase n in the Drake equation.
    1) Kepler has found that there are lots of planets around other stars, something the DE hoped for but didn't really know.
    2) As Julia said, there used to be lots of flowing water on Mars, and a lot of it is still there frozen
    3) Moons of Jupiter and Saturn (Europa and Enceladus) powered by tidal forces seem to be decent candidates for life. The habitable zone of stars has thus widened.
    4) The extremophile argument is a good one and Massimo's dismissal of it, along with everything else to do with SETI, suggest that he is simply doesn't like it.
    5) The early beginning of life in Earth's history suggests life gets going easily when conditions are non horrific.
    6) The existence of life on earth is significant in that it simply shows that tech life is possible. If we were speculating on another universe, a bubble universe with favorable physics, and we did not know of a single example of life, our opinion as to whether that universe might have life would obviously be helped by knowing there is an example of it -- and hurt by not knowing of an example of it.

    It seems to me that Seti is worthwhile simply to see if tech life might be found easily and that, as M and J discussed, not finding it doesn't mean it isn't there. The most damning thing to me is that we aren't being visited.

    PS Why the preoccupation with whether SETI is science or pseudo science? Isn't it at least a pursuit that is intellectually reasonable, never mind the label?

  10. Ian, thank you for your reply. "Uncertainty robustness" is an expression I gratefully adopt from prof Yakov Ben-Haim*, telling us to replace the usual utility optimizing in making decisions, by a normative "good enough" approach, in selection outcomes that will have enough robustness against uncertainty of what we might (not) encounter along the way to get there. Outcomes most robust must be our favorites. SETI might be the only way to get to know if there is extraterrestrial intelligence robust enough to withstand arguments as though it would be invaluable, considering the costs compared to other options?


  11. [I meant to address Massimo Pigliucci, not Ian Pollock. Sorry Ian, my mistake. Apologies.]

  12. It is true that when something really does not exist, one might spend a long time futilely looking for it. Many people have spent enormous energy searching for lost tribes, lost gold, and lost kingdoms. SETI might be yet another example; I don't know. Why is it so difficult to decide that what you're looking for really isn't there? The answer, ironically, is that the world has endless possibilities for discovery and surprise. I discuss this in a short non-technical essay: Beware the Rareness Illusion When Exploring the Unknown

  13. Massimo, you mention that you are sure that most physicists would not argue with the idea that the universe is filled with skateboarding teenagers. You are wrong if you are talking about an infinite universe. Many physicists believe that if the universe is infinite (which it seems to be) and the combination of atoms that makes up us and our planet must repeat again out there. So, there are infinite numbers of skateboarding teenagers out there. Sounds like nonsense to me to, but you are talking about the multiverse and the physicists that are working on it. Brian Greene discusses this type of multiverse in his newest book, The Hidden Reality.

  14. zubarsky,

    you seem to be confusing the universe with the multiverse. The universe is not infinite, since it had a beginning 13.6 billion years ago and has expanded at a finite speed ever since.

    The multiverse is a conjecture among others, with no empirical bases so far (and likely ever), so you will excuse me if I treat it as such.


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