Contemporary Work on Emergence: The Life-Body Problem
The Normative Nexus and the Nature of Functional Stability James Barham University of Notre Dame ISHPSSB Brisbane, Australia July 14, 2009 Teleology Is Back Remarkably, it has recently become almost respectable to argue that a proper understanding of human beings requires taking teleology seriously Not just in human thought and action, but in biology generally Foot (2001), MacIntyre (2006), McLaughlin (2001), Nagel (forthcoming), Okrent (2007), Schueler (2003), Sehon (2005), E. Thompson (2007), M. Thompson (2008), Walsh (2006), Weber & Varela (2002), Zammito (2006)
Of course, the first thing one might ask about this claim is what it means to take teleology seriously Taking Teleology Seriously? Epistemological Approach Teleological explanation in biology is non-optional, But this tells us more about the peculiarities of human cognition than it does about life as such Disunity-of-Science Approach Unity of science is a chimera; many different forms of explanation flourish independently Teleological explanation in biology is just one of these Realist Approach Teleological explanation in biology is non-optional,
Because it corresponds to an objectively real, physical principle What Teleological Realism in Biology Means Realism about teleology in biology essentially means: The explananda corresponding to teleological explanations enjoy metaphysical parity with those corresponding to mechanistic explanations (Walsh forthcoming) In other words, realism about teleology in biology is the claim that: Teleology is not just an explanatory principle There is also a corresponding metaphysical principle that ought to be investigated as an explanandum in its own right Assuming the Realist Approach In this talk, I will assume the realist approach
I will not argue for its superiority over the other two main approaches However, I acknowledge that the realist approach is the most controversial one, with the heaviest burden of proof Two main aims of this talk: To motivate a particular characterization of teleology in biology To argue for the plausibility of this characterization Teleology and Consciousness I will ask you to take one more assumption for granted: Although our paradigm of purposiveness is human conscious action, nevertheless, the purposiveness of human action and its conscious, subjective, or experiential quality are conceptually distinct See
Bedau (1990) Therefore, the teleological phenomena associated with life as such may or may not be essentially linked to consciousness, as a matter of nomological fact Here, I will simply bracket the question When I speak of teleology in biology, no assumption of accompanying subjective experience ought to be inferred Is There a Normative Survival Principle? At the heart of the realist approach to teleology in biology is the claim: Biological survival* is a normative concept; therefore, on the assumption of realism, there exists some real physical principle corresponding to the
normativity of biological survival Let us look at some arguments pro and contra this highly controversial claim Note: The notion of survival as I use it here encompasses both metabolism the functional organization ensuring the perpetuation of the token physical systemand reproductionthe process (which is itself a particular instance of metabolism) ensuring the perpetuation of the type physical system. Arguments Pro a Normative Survival Principle It certainly seems as though survival were a normative concept Colloquial function talk Feeding, fleeing, fighting, reproducing, struggle for survival, etc. Biological talk Goals, purposes, functions, information, messages, signals, codes, computing, proofreading, editing, etc. (see any textbook) Increasing use of term intelligence
Capacity to choose appropriate means to an end Bray (2009), Jonker et al. (2002), Shapiro (2007) All of these ways of describing biological phenomena are normative They all imply a standard of success/failure, correctness/error, etc. Ultimately, they all presuppose the normativity of survival Lowes Analysis of Action In addition, it is striking that many conceptual analyses of human action may be applied more or less without alteration to living processes as such Consider, for example, E.J. Lowes analysis of practical action, in the broad sense of instrumental rationality: Just as a true belief is one which corresponds to fact, so a good action is one which corresponds to need. In another idiom, just as facts are the truthmakers of true beliefs, so needs are the goodnessmakers of good actions. (Lowe 2008; 209; original emphasis) Survival and Needs
Obviously, the concept of needs in Lowes account is itself in need of further analysis Lowe postpones that question, but says he holds out no hope that a naturalistic account of need can succeed (Lowe 2008; 212) For our purposes, needs may be understood in relation to survival A dog has need of water in order to survive; thus, drinking water is a good for the dog because it contributes to its survival What is important is to see that conceptual analyses of human instrumental rationality are directly applicable to living processes as such I will pursue this idea further in a moment But first let us begin the task of looking at the notion of survival from a physical point of view
Survival as Dynamic Stability A living thing is a physical system of the nonequilibrium- thermodyamic (dynamic) type Hurricanes, candle flames, other dissipative structures For a living system to survive is for it to persist as the kind of dynamic physical system that it is With a lifespan that is long compared to its thermodynamic relaxation rate For any sort of physical system to persist is for it possess a sort of stability For a dynamic system to persist is for it to possess a type of dynamic stability Therefore, a living system possesses a type of dynamic stability
The Notion of Functional Stability However, the type of dynamic stability possessed by a living system is different from that possessed by any non-living system The latter always boils down to free energy minimization In contrast, living systems draw on internal energy stores to act on the world to satisfy their needs The type of dynamic stability possessed by living systems implies the concept of action Individual goal-directed actions may be termed functions Therefore, we may call the type of dynamic stability possessed by living systems functional stability The Normative Nexus Survival is ultimately normative for living systems
Normativity of survival implies ultimate goal-state (purpose) to be aimed at Call it Z Survival (functional stability) cannot be achieved without specific actions (functions) Action-requirement implies needs (such as drinking water) Call it X Needs imply means-end relation and hypothetical necessity X is needed (required) for Z Hypothetical necessity implies instrumental ought If Z is to obtain, then X ought to occur Needs and means-end relation give rise to value ( la Lowe) X is good in case it contributes to Z Drinking water is good (e.g., for a dog) in case it contributes to survival Call this web of relations among survival, action, purpose, need, instrumental ought, and value, the Normative Nexus This analysis works equally well at any level of the functional hierarchy
Example: Bacterial Chemotaxis For example, take bacterial chemotaxis (Stock & Surette 1996) An E. coli bacterium transitions between two motility states, running and tumbling Running is smooth, linear motion produced by turning the flagella counterclockwise Tumbling is random motion produced by turning the flagella clockwise When a cell senses it is moving up an attractant (or down a repellant) gradient, it reduces the rate of tumbling, resulting in net movement towards (or away from) the source It is quite natural to say: A bacterium needs attractants (typically, a food source) to survive Similarly, it needs to avoid repellants (typically, poison) to survive Its purpose in swimming up (or down) a gradient is to find and consume attractants (or avoid repellants) The flagellar mechanism is the means to this end
A bacterium ought to move toward attractant and away from repellant sources Moving up an attractant (or down a repellant) gradient is good for a bacterium All of this presupposes that bacteria can distinguish attractants from repellants Bacteria partition their world into axiological categories: Arguments Contra a Normative Survival Principle Incredulous stare The Normative Nexus is just anthropomorphic projection It trades on equivocation Normativity is properly attributable only to human reason Survival, properly understood, is not a normative concept
Organisms are simply machines whose parts were put into place by natural selection By accident, some organisms happen to attain novel configurations of their parts that happen to result in differential reproduction Call this the Reduction Claim Functional stability does not correspond to any single physical principle, but is only a congeries of disparate physical and chemical processes A normative survival principle is inconsistent with everything we know about biology and physics Call this the Science Objection Reply to Incredulous Stare
The charges of anthropomorphism and equivocation essentially beg the question Whether normativity is properly attributable to survival and other living processes is the issue Besides, the Normative Nexus analysis works Normative language makes perfect sense applied even to bacteria Indeed, it is indispensable It is virtually impossible to avoid normative language in biology Why would this be the case, if the Normative Nexus were nothing more than an equivocation? But what about the Reduction Claim? Reply to Reduction Claim To repeat: the Reduction Claim is that we
already have a successful mechanistic reduction of teleology and normativity in biology Namely, we know that organisms are simply machines put into place by natural selection Three ways of replying: Argument from History Argument from Petitio Argument from Extreme Plasticity Argument from History History (in this case, selection history) is not the right kind of concept to explain a dynamical property like functional stability To speak of the history of a physical system is a short-hand way of referring to the sequence of states it traverses But it is the dynamics of the system and surround that explain this sequence, not the other way around
Examples: amorphous solids (glass) vs. crystals, stars In one sense, they are history-dependent But that just means they are dependent on the particular details of their dynamical evolution Argument from Petitio It has been pointed out repeatedly that the theory of natural selection presupposes the functional organization of organisms, and so cannot explain it A functionally coherent organism must already exist before it can be selected See, e.g., McLaughlin (2001), Walsh (2000, 2007) It is equally well-known that the concept of a machine also begs the question of normativity Machine is a normative concept
A machine is something that performs a function But nothing in the concept of a machine is capable of explaining which system state counts as the functional state See, e.g., Nissen (1997) A Recent Elaboration of the Petitio Argument Recently, West-Eberhard (2003, 2005) has further refined the Petitio Argument Even if genetic changes are always random,* phenotypic changes never are Because between the genotype and the phenotype is the teleological
process of phenotype construction Therefore, whatever is subject to natural selection has already been teleologically constructed This is a general point about all living things However, it is powerfully demonstrated by examples of extreme plasticity *Note: This now seems questionable (Jablonka & Raz 2009; Shapiro forthcoming), but there is no time to discuss this issue here A Note on Terminology The phenomenon in question goes by many different names: Robustness, plasticity, adaptive capability, phenotypic accommodation, etc. Terminology inconsistent
The basic idea is spontaneous compensation following perturbation to maintain viability Two ways: Recovery of old steady state (robustness) Homeostasis, healing Attainment of new steady state (plasticity) Three-legged dogs gait A term to encompass both is metastability Equifinality Bifurcation Examples of Extreme Plasticity Cases of successful compensation following massive perturbation of: visual system in humans (Bach-y-Rita 1995; Ptito et al. 2005)
in mice & ferrets (Tropea et al. 2009; Von Melchner et al. 2000) in flies (Heisenberg & Wolf 1984) locomotory system Slijpers goat (West-Eberhard 2003, 2005) Involves extensive remodeling of neural, skeletal, and muscular systems single cells Adaptation in isolated hepatocytes (Baker et al. 2001; Elaut et al. 2006) These capacities are inexplicable on mainstream view These specific capacities cannot possibly have been selected for Positing selection for such a general capacity would concede the point at issue: Life as such has a universal capacity for goal-directed compensation
Reply to Science Objection The Science Objection says: A normative survival principle is inconsistent with everything we know about biology and physics Three ways of replying: A simple argument to show that a stability principle for living things should be expected System-level models of cooperative phenomena in biology Theoretical proposals for a normative survival principle Together, these responses show that the existence of a normative survival principle is not implausible in light of contemporary science A Stability Principle Should Be Expected The following simple argument shows that we should expect there to be a physical principle underlying the functional stability of living things:
All naturally stable systems derive their stability from an underlying physical principle Organisms are naturally stable systems Therefore, organisms derive their stability from an underlying physical principle The idea that organisms lack any unifying principle is highly suspect, from a physical point of view System-Level Models of Cooperative Phenomena in Biology Following are some system-level models of cooperative phenomena (long-range coherence and coordination) in biology Brain Function (Freeman 2001; Freeman & Vitiello 2006) Motor coordination (Jirsa & Kelso 2004; Kelso 1995; Warren 2006) Cancer as a tissue-level disorder (Sonnenschein &
Soto 1999) Metabolic networks (Barabasi & Oltvai 2004; Csete & Doyle 2004; Wolkenhauer et al. 2005) Coordination of muscle contraction (Pollack 2001) Two Theoretical Proposals Two specific theoretical proposals have been made for modeling a normative survival principle Christensen & Bickhard (2002) Di Paolo (2005) Both of these proposals involve cashing out the notion of autopoiesis (self-production) in terms of nonlinear dynamics This is surely a step in the right direction However, while something like these proposals may be necessary for understanding a normative survival principle, they are not sufficient
The Trouble with Nonlinear Dynamical Models No theoretical proposals drawing on nonlinear dynamics alone can be sufficient for modeling a truly normative survival principle Nonlinear dynamical models as such are phenomenological We need to connect them up with underlying physical principles Adding nonequilibrium thermodynamics into the equation does not help, either Dissipative structures still just minimize free energy We need a way to distinguish functional stability from hurricanes, candle flames, etc. A Way Forward
Morrisons (2006) version of emergence* may offer a way forward She points to what she calls theoretical principles that are used to explain how stable states of matter can exist and yet be autonomous (in the sense of insensitive to the details of the lower-level dynamics) Spontaneous symmetry breaking Renormalization Group Critical phenomena (phase transitions, etc.) Effective field theories But why should we think that any of this is relevant to biology? *Note: The notion of emergence is many-faceted and controversial; however, the main objection that any strong (ontological) version of emergence must violate Kims causal exclusion principle has been persuasively rebutted by Perovic (2007).
Aspects of the Living Phase of Matter Cytoplasm has the following characteristics: Extreme crowding (Luby-Phelps 2000; Wheatley 2003) Gel-like properties (Pollack 2001) Liquid-crystal-like properties (Ho et al. 1996) Phase transitions important to macromolecular function (Pollack 2001; Pollack & Chin 2008) In addition, proteins are: Dynamically active (frustrated) systems (Frauenfelder et al. 1999) Functionally coupled to the cytoplasm (Frauenfelder et al. 2009) These facts support the idea that Morrisons theoretical-principles-based emergence may be involved in the living phase of matter The Nature of Functional Stability The idea, then, is that the universal theoretical principles would provide some continuity across emergent levels Example: spontaneous symmetry breaking While a new particular law and/or conservation principle
would come into existence with each new type of existent Life would require its own conservation principle corresponding to the property of functional metastability This statement by Hiroaki Kitano nicely expresses what is needed: The key issue is whether it is possible to find a formalism in which robustness and its trade-offs could be defined so that robustness is a conserved quantity (Kitano 2007; 3; emphasis added) Normative Survival Principle Not Unscientific If such a formalism could be found, then a rigorous theoretical explanation of the normative survival principle might be possible Because the functional metastability of life would be based on its own conservation principle, this proposal
would not be tantamount to reducing life to another principle, like the conservation of energy Given what we know about biology and physics, the existence of an emergent principle governing the sui generis functional dynamics of the living phase of matter is not out of the question (Laughlin et al. 2000) The very existence of such theoretical proposals shows that the idea of a normative survival principle is not Conclusion Extending theoretical principles derived from fundamental and condensed-matter physics to encompass the living phase of matter seems to offer the best hope of giving an adequate scientific account of the normative nexus and the functional metastability of living things References
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