Multivers: Mondes Possible de l’Astrophysique, de la Philosophie, et de l’Imaginaire

While I was in Paris recently I picked up several French books that aren’t readily available in the US. One of these is entitled Multivers: Mondes Possible de l’Astrophysique, de la Philosophie, et de l’Imaginaire, and it takes the form of a conversation between theoretical physicists Aurélien Barrau and Jean-Philippe Uzan, as well as historian of science fiction Patrick Gyger and philosopher Max Kistler. Astrophysicist Isabelle Joncour acts as moderator. The conversation is often dominated by the provocative philosophical flights of fancy of physicist Barrau, with philosopher Kistler playing the role of providing sobriety and down-to-earth arguments.

The contrast with the typical Multiverse Mania books of the Anglo-Saxon world is striking. French intellectuals are seriously educated in philosophy, and think it natural to carry on arguments invoking the ideas of a wide range of philosophers, even in contexts such that similar Americans wouldn’t see the point of raising philosophical issues. In this case, some of the discussion revolves around the ideas of American philosophers David Lewis and Nelson Goodman about “possible worlds”. It’s amusing to note that it would probably be extremely difficult to get together for a discussion a group of American physicists who had even heard of these two of their countrymen, much less be capable of seriously discussing their ideas. Maybe that’s just as well though, as professional philosopher Kistler makes a good case that the “possible worlds” at issue in this sort of philosophy don’t really have anything to do with the multiverse.

Barrau takes a position refreshingly agnostic about string theory and LQG, deploring the ideological warfare between them. Unlike most physicists though, who were interested in string theory when it might have predicted something and are now losing interest, he claims that the fact that it can’t predict things is what got him to really like string theory:

la theorie des cordes commence à m’intéresser à partir du moment où, précisément, elle prend ce tournant où l’on ne sait plus très bien où on va et où on change les règles du jeu au milieu de la partie. Ca devient très motivant!

string theory starts to interest me precisely from the moment where it takes this turn; one doesn’t much know where one is going and one changes the rules in the middle of the game. This starts to become appealing!

For Barrau, it’s just when string theory starts to turn into pseudo-science that it interests him. In brief, he agrees that the string theory multiverse moves the field from physics into metaphysics, but thinks that’s a good thing. He’s in love with the idea of finally being free from many of the conventional constraints physicists labor under as they try to do science and the possibility of taking up again the overlap of some French philosophy with science that Alan Sokal very successfully made a joke of. He starts out:

En philosophie francaise, je pense à Deleuze et à son rhizome, au “plus d’un” de Derrida, au(x) toucher(s) chez Nancy, au nominalisme de Foucault, a l’ontologie du multiple de Badiou…

and immediately realizes that the question of Sokal must be addressed if you’re going to go on like that:

Je crains que l’on soit encore dans une sorte de timidité généralisée qui est peut-être issue des contrecoups de la triste affaire Sokal. Il est tout à fait souhaitable d’enjoindre les gens a ne pas dire n’importe quoi. Cela ne se discute pas. Mais il serait dommage que cet excès de précaution leur interdise tout simplement de penser à partir des constructions scientifiques. La physique d’aujourdhui me semble fabuleusement propice à philosopher, il faut oser.

I fear that we’re still in a kind of generalized timidity that may have come about as a consequence of the sad Sokal business. It’s completely desirable to insist that people not say just anything, that’s not up for discussion. But it would be a shame if too much caution keeps them from thinking starting with scientific constructions. Contemporary physics seems to me fabulously propitious for philosophizing. One must be daring.

There’s much abuse directed towards Popper, falsifiability, and of crude attempts to separate science from non-science. Barrau is very happy with the idea of not having any way of distinguishing the two, while Kistler tries to remind him that, tricky as it may be, there’s an important distinction involved. What seems important to me here is maybe more of a sociological than philosophical point, and it’s a bit like the one that motivated Sokal. If you don’t have any standard at all for what is science and what isn’t, you lose control of the powerful role of science in how we see the world, and put yourself at the mercy of socially stronger forces who will be happy to take on this role and grab control and power away from those who have disarmed themselves. In the specific local area of fundamental physics, if there’s no way to recognize that ideas have failed, those with a vested interest in a set of failed ideas will never give up their control of the discourse. Instead of the philosophers listed by Barrau, someone like Michel Foucault might be more relevant…

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10 Responses to Multivers: Mondes Possible de l’Astrophysique, de la Philosophie, et de l’Imaginaire

  1. Kea says:

    A courageous, but futile new direction for NEW. It’s not like the French only discovered philosophical rationalism yesterday. They have been mocking this kind of Anglo-Saxon idiocy since the revolution, which is probably why they are blind to the good neo-Popperian arguments.

  2. Dr. Philip Carey says:

    Peter, your comments regarding the familiarity of American physics professors with modern philosophy are wholly inconsistent with my experiences at several large American research universities. In my current department, for example, lively and sustained conversations about philosophy and physics are a daily treat, both with grad students and with faculty. Indeed, a number of professors in my department have masters in philosophy; one has a doctorate. Please avoid making such generalizations in the future!

  3. The Cosmist says:

    Doesn’t the “philosophication” of physics represent the decline and fall of the field? Aren’t you be back to the days of Zeno and Aristotle contemplating the universe abstractly without contact with reality? And to philosophize a bit myself, will anyone care about the laws of physics in a post-Singularity world of infinite reality simulations and arbitrary physical laws in the Dyson sphere computronium hive-mind of the future? 😉

  4. Peter Woit says:

    Philip Carey,

    American academia is a huge and wonderful place, and I don’t doubt that somewhere it includes physicists able and willing to knowledgeably discuss David Lewis and Nelson Goodman. But personally I don’t seem to have run across these people. It is true that I spend less time amongst physicists than I used to, and maybe since the advent of the multiverse, such discussions of “possible worlds” now are common in American physics departments, who knows…

  5. Peter Woit says:


    OK, I have to admit I was wrong about this. It was kind of a mistaken attempt though to defend the honor of American theoretical physics. I should have known better.

  6. Bee says:

    That’s interesting, thanks. I was wondering the other day what’s the history of the multiverse-idea? I mean, most modern ideas turn out to have been touched upon much earlier. Is there anything in the books about it?

  7. Dear Peter,
    Thanks for your interest in our book. This is much appreciated.
    If I can allow a few comments, I have not said that “string theory is a pseudo-science”, nor that it is “metaphysics”. What I think is that it is both impossible and uninteresting to try to define the borders of science. Which does not mean that “everything is the same”, of course. Clearly, string theory plays with the limits of physics and I indeed find this interesting.
    However, on this specific string theory point, I would like to emphasize that one can work on Loop Quantum Cosmology (this is the case for me) but still highly respect string theory and consider this approach as beautiful and meaningful. The World is highly diversified and so are our models !
    Best regards,
    Aurelien Barrau

  8. peterg says:

    “I think is that there is both impossible and uninteresting to try to define the borders of science.”

    The first part probably is correct, but I respectfully disagree with the second part. Maybe I’m missing the point, but it is as if you’re saying that morality is not grounded in rational thought (I agree) and that therefore rational discussions about morality are uninteresting (wrong, in my view).

    A long time ago I collaborated with physics researchers. I lost track of most of them, but I’m certain one of them (a mathematical physicist) has asked “Yes, it’s nice, but is it physics?” when he learned about the more esoteric domains of string theory.

    Perhaps more scientists should have asked that question, even if there is no straight answer.

  9. Peter Woit says:


    Thanks for the clarifications. I should have made clear that the use of “pseudo-science” was my own editorializing, and shouldn’t have been attributed to you.

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