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.

Thursday, July 24, 2008

Kauffman on emergence and reductionism

Since people have asked, here is my take on Stuart Kauffman’s ideas on reductionism and emergence. Kauffman distinguishes between two types of emergence, “epistemological” and “ontological.” Epistemological emergence is the idea that complex systems cannot be described, as a matter of practice, in terms of their component units because of our epistemic limitations, that is our inability to do the computations. According to ontological emergence, on the other hand, a full understanding of complex systems in terms of their components is not possible in principle, not just because of practical considerations, because new levels of causality appear at higher levels of organization.

To take my favorite example, an engineer working on the Brooklyn Bridge, epistemological emergence would say that the engineer cannot work at the quantum mechanical level because he doesn’t have sufficiently powerful computers and enough time in his schedule to do so, but it would be possible in principle. But if ontological emergence is true, then the engineer better work at intermediate, macroscopic levels of analysis, because those are the causally relevant ones.

Kauffman sees ontological emergence as more powerful than the epistemological flavor, and he subscribes to both (well, the first one logically entails the latter anyway). But more powerful to what end? To defeat reductionism, for which he accepts physicist Steven Weinberg’s definition: “the explanatory arrows always point downward.” Reductionism of this sort is problematic for various reasons, according to Kauffman, including that with it “comes the conviction that a court proceeding to try a man for murder is ‘really’ nothing but the movement of atoms, electrons, and other particles in space.” Kauffman is really worried about free will.

Part of the problem here is that it is hard to define what emergence is. I stick to the basics and think of emergent properties as those properties arising from non-linear, non-additive interactions among the component parts of a system (as the popular refrain goes, “the whole is more than the sum of its parts,” because there is something due to the multiplication or other mathematical operations among parts). The advantage is that one can then measure the degree of emergence quantitatively, for instance using statistical tools like the analysis of variance.

Kauffman describes three examples of emergence: the origin of life, the origin of agency (i.e., the capacity of making decisions), and the origin of consciousness. I find all three examples poorly chosen. While there is no question that plenty of non-linear interactions are involved in systems that have made each of these three transitions, unfortunately we understand the transitions themselves very little. It is hard to imagine how one can explain a mystery (emergence) with an enigma (the origin of life, agency or consciousness).

I have often discussed two of my favorite, much more mundane, examples, which I think allow for a better grasp of emergence, and help eliminate the aura of spooky mysticism that often surrounds the topic: water and houses. The properties of the molecular form of water are not the simple sum of the properties of the individual atoms of oxygen and hydrogen that make up that molecule. The reason for this is because new properties emerge into the system once we combine atoms of a given type in a certain spatial arrangement, and then again once molecules in turn interact as higher (than atoms) units. Sure enough, physicists and chemists have historically had a really hard time trying to predict the physical-chemical properties of water from first (quantic) principles, though we can understand and describe them when the analysis shifts to the (higher) molecular level. Even if they will eventually succeed, remember that water is just about one of the simplest examples of emergence one can think of, many many orders of magnitude away from the stuff Kauffman is interested in.

The example of the house is due to Richard Lewontin, and was originally meant to explain the difference between gene-environment interaction (my technical area of expertise) and simple nature-or-nurture thinking. If you build a house of bricks and lime, you could, in principle, ask what the relative contribution of the two components is to the finished edifice. You might, for instance, simply weigh the bricks and the lime, and conclude that X% of the house is “due to” the bricks and Y% is “due to” the lime. But you would be spectacularly missing the point, of course, because a house is not just the sum of a certain number of bricks and a certain amount of lime, it is the result of a precise pattern of alternative laying of bricks and lime. (Substitute “genes” for bricks and “environment” for lime and you get Lewontin’s original point.)

Kauffman faces a second problem with his rather simple definition of reductionism (borrowed from a physicist, nonetheless!). For instance, one can easily concede material reductionism, the idea that everything is made of the same “stuff” (quarks, strings, whatever), without having to go so far as agreeing to process reductionism, the very different and much stronger proposition that causation always originates only at the bottom level.

It would be silly to deny material reductionism, unless you happen to be a mind-body dualist (virtually no scientist is, and very few philosophers). On the other hand, it seems to me that the idea that “the explanatory arrows always point downwards” is pretty difficult to defend. While causality certainly is a slippery notion, the “cause” of, say, the recent woes of the housing sector in the United States is best understood at the level of human individual and societal interactions, not at that of quarks (of which humans, indubitably, are made).

So it is in fact true, from the point of view of material reductionism, that a court proceeding to try a man for murder is ‘really’ nothing but the movement of atoms, electrons, and other particles in space. But to mistake that for a successful example of process reductionism would be precisely like being satisfied with the explanation of a house in terms of counting bricks and weighing lime.


  1. The account of reductionism strikes me as misguided. Who thinks there's something special about linear processes and makes a deep philosophical commitment to them? The key plank in reductionism, beyond what you call material reductionism, is that all the parts will follow the laws of physics. If you look back in the history of science, before the advent of quantum chemistry, a lot of people thought there might be special laws that governed, say, the behavior of water molecules, that had nothing to do with the laws governing atoms individually. Of course, there's further debates about how to make sense of high level properties, but the talk of "linearity" doesn't seem to capture any interesting debate.

  2. hallq,

    well, sorry you didn't find my account of reductionism useful. Do you have a better working definition of reductionism and of emergence?

    The issue is not with the basic laws of physics: everyone (well, except dualists) agree that they hold at all levels. The question is whether there is new causality at higher levels, on top of the laws of physics.

  3. You were right, gelato is much better than reductionism, but I've only had vanilla bean, mocha chip, and cinnamon.... But I digress to the matter at hand, I would say that understanding something at quantum levels is not necessary for many (most) things. I would say, however, that epistemological emergence seems to be the more likely of the two. Ontological emergence seems to be an intellectual cop-out.
    And to continue my previous thought: I would really like to try dark chocolate gelato.

  4. The way I define "emergent property" when talking about it is very simple (I think) and goes something like this: "an emergent property is something that is not a property of the constituent parts, and can't be predicted from them".

    And the discussion usually ends at the "ontological x epistemological", although we have never used these terms in our discussions -- we discuss these things in my lab and adjacencies as the laypeople we are in this field. For fun, y'know. :-)

    Or, as we say, we can't predict because we just don't know enough yet (my boss' position, usually), or because it is intrinsically unpredictable (the position I usually take).

    Water is my favorite example too. Some people get a little confused about their levels of explanation, here, and think we know it all. They think we can predict whatever we want about water. Except we can't, from first principles. So we do have astonishingly repeatable measurements about all kinds of things water, and we can thus "predict" things. But people forget this is actually empirical data, not ab initio, real prediction.

    Who is right? I myself have no way of telling, I keep my plate pretty full with the struggle to stay abreast of my own research fields. But if Robert B. Laughlin ("A different universe, reinventing physics from the bottom down") and Ilya Prigogine ("The end of certainty, time, chaos, and the new laws of nature") are happy to take the ontological emergence position (as I think would be the case from reading their books), who am I to disagree?

    (note: this could be seen as an argument from authority; well, I happen to see it as an argument from competence) :-)

  5. Anyway, even accepting ontological emergence, I don't really see how that would rescue free will (note to self: maybe I should read Kauffman's books, how about that?). At least not in a way that people would like, at least.

    Because, as I see it, accepting stochasticity and non-linear interactions (i.e., nearly all interactions) leading to genuinely unpredictable, emergent properties does not really make me free to choose between strawberry and chocolate ice cream. It might lead me to make a choice that is random, even if constrained by my previous experiences; maybe, but I don't think that's what people would like to hear. Or it would lead to an unpredictable (from first principles, e.g. the position of all particles in my brain, or even the neural firings of all my neurons at the moment) answer, but one that would be as determined by the immediate circumstances as water's properties, even if genuinely emergent.

    My U$0.50 worth (inflation is a terrible thing)

  6. J,

    we are in agreement on both points. I am not completely sold on ontological emergence, but I'm willing to bet a (small) sum of money on it. And no, it doesn't get you free will...

  7. Hello, Prof Pigliucci, an interesting post. My past and continuing education isn't in biological philosophy, but that does not in any way prevent me from wading into this interesting discussion. I do not want to sound pedantic, but I feel what Kauffman means by "epistemic" emergence is actually "methodological" emergence. For instance in the Brooklyn bridge example, the inadequacy of methods or techniques at the quantum mechanics level prevent the engineer from computing whatever he wishes to predict about the systems properties of the bridge. An analog in biology would probably be that the methods used to investigate problems in developmental genetics, are insufficient to solve problems of developmental systems biology.
    By epistemic emergence, I think what can be meant is that the body of knowledge- the rules, laws and predictions, that are applicable to a process (probably both in a causative and effective sense) do not apply to a more fundamental level/process. Applied to the example of the engineer, even if he does possess the necessary and sufficient computational tools, can he predict the behavior of the bridge on the basis of the physics of its various components?

  8. Ramray,

    thanks for the post. Yes you can call epistemic emergence methodological, if you'd like, I just stuck to Kauffman's original terminology in the post. However, for the other type I think Kauffman's term of ontological is more accurate, because "epistemic" in philosophy denotes the limits of human knowledge, not essential facts about the nature of the world (as in ontology).

  9. Prof. Pigliucci,

    I’ve been reading your blog for the last year or more – off and on – and have quite enjoyed and appreciated them; thank you.

    However, I notice, based on your own “conversion on the road to Damascus” relative to Eugenie Scott and “methodological and philosophical naturalism”, that you’re not dogmatic about your positions and permit their evolution. So from that point of view I’m curious about your position and comments on “mind-body dualism”, “material reductionism” and the “epistemic limits of science”.

    Specifically, it seems to me that conceding those limits is tantamount to conceding dualism in general, if not the mind-body type in particular. Relative to which, you made reference to Lee Smolin’s “The Trouble with Physics”, an excellent book, both for the overview of string theory and the state of physics and for its description of the effects of group-think therein. But Smolin starts off by noting that one of the “five great problems in theoretical physics” – and a “tremendous embarrassment” – is that the standard model has about 20 parameters from which the model follows but which also do not have any justification – “we have no idea why these numbers have the values they do” [pg 13]. While I don’t think he actually makes this conclusion it seems to me that it is in “the nature of the beast” that we have such dichotomies, such dualisms, the traditional one being, I think, “the unmoved mover” and the related question of where “god”, the first cause, came from.

    And along the same line is Richard Dawkins in his The God Delusion and his related TED talk [http://www.ted.com/talks/richard_dawkins_on_our_queer_universe.html, based on a reference to J.B.S. Haldane’s "My own suspicion is that the universe is not only queerer than we suppose, but queerer than we can suppose"] in which he argues that “the human frame of reference limits our understanding of the universe”.

    Also, there are the books by Paul Davies [God & The New Physics] & S. Jonathan Singer [The Splendid Feast of Reason] in which they argue that the central principle of the wave-particle duality in the theory of quantum mechanics is generally reflective of those same limitations: we will always have these incommensurable and irreconcilable systems of thought, or sets of phenomena that are not explainable in a single one. Maybe further evidence on the nature of emergent properties.

    But whether that actually translates specifically into mind-body dualism is, I think, debatable, but I certainly don’t think it is a foregone conclusion that it doesn’t which your “silly to deny material reductionism, unless you happen to be a mind-body dualist”, apart from apparently being inconsistent with “epistemic limits”, would seem to suggest is the case. Not that I’m arguing or trying to suggest that the phenomenon of consciousness is anything other than natural – “supernatural” being, it seems, a contradiction in terms, like a “square circle”.

    I gather that you’re not particularly impressed by David Chalmers’ philosophy, or by his haircut, but I thought his arguments, in his “The Conscious Mind”, were a reasonably broad and thorough survey of the then existing [1996] theories and concepts and research on the phenomenon. But I also thought quite cogent and intriguing his argument that there is some “uniform property of the universe”, some attribute of reality, not explicitly definable in terms of any science, that leads to the existence of consciousness at least as an emergent phenomenon.

    Although it really is, I find, quite interesting and fascinating that these questions, these “intimations of immortality”, exercise the minds of so many. As I believe you suggested in your blog on Martin Gardner, the concept of an “eternal soul” is at least a tenacious meme. Though not necessarily, I think, without value or potential realization. As the aphorism has it: “Man’s reach must exceed his grasp, else what is Heaven for?”



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