Metascience (2010) 19:441–444 DOI 10.1007/s11016-010-9427-y BOOK REVIEW
Complex science for a complex world Sandra D. Mitchell: Unsimple truths: science, complexity, and policy. University of Chicago Press, Chicago, 2009, x + 149 pp, US $27.50 HB Bruce R. Long
Published online: 7 August 2010 Ó Springer Science+Business Media B.V. 2010
Sandra D. Mitchell argues that traditional science fails to attain adequate understanding of complex natural systems. She asserts that such systems resist uniform reductive strategies of investigation and analysis because they have multiple levels of complexity and are non-linear and non-deterministic to such an extent that traditional statistical predictive analyses fail. Mitchell offers integrative pluralism as an alternative pluralist and pragmatic framework for scientific epistemology. Integrative pluralism is proposed as a pragmatic strategy that retains scientific realism but uses a ‘‘pluralist–realist approach to ontology’’ as conducive to more effective science and better science-guided policy. This approach is seen as superior to less flexible predict-and-act models that deflect scientific defeasibility. Unsimple Truths contains insightful arguments for integrative pluralism as conducive to scientific defeasibility in policy. Computer simulation is given a central role as necessary for the classification of complex systems as emergent, and as a central practical tool for analysing complex systems. The negative thesis about the inadequacy of traditional science is comprehensive, while the positive integrative pluralism thesis is presented in a somewhat pre-theoretic meta-scientific manner. A more rigorous formulation and a demonstrative situational presentation of the strategy itself may have convinced me more of the advantages of integrative pluralism over existing scientific strategies, which incorporate contingent defeasibility. The introduction and chapter two are devoted to the difficulties that complex natural systems present for static universalism and wholly reductive strategies (22). However, conventional commitments to scientific rigour are seen neither as defective nor as dispensable, only as ineffectual when inappropriately applied to such systems. Empirical science is embraced and arbitrary pluralism eschewed (109). Integrative pluralism is not formulated as an anti-reductionist strategy, but rather offered as a pluralist approach to explanatory strategies. Mitchell’s claim is B. R. Long (&) Department of Philosophy, The University of Sydney, Sydney, NSW 2006, Australia e-mail:
[email protected]
123
442
Metascience (2010) 19:441–444
that thoroughgoing strong reductionism fails to account for many results associated with complex natural systems. Of particular relevance are the kinds of complex systems that exhibit emergence, which Mitchell thinks are common. Correspondingly, she argues that Jaegwon Kim’s reductively motivated ‘‘minimalist to eliminativist’’ argument against ontological emergence is flawed on the basis of descriptivist assumptions and because it ‘‘ignores the essential partiality of representation’’ (31). However, it is not obvious that Kim’s thesis embraces universally existing descriptions as a requirement, and his functional reductionist strategy seems to be designed to answer the problems of partial representation or at least to accept it. Mitchell considers emergent properties of complex systems as not aggregative: the properties of the whole are not a simple aggregate of the properties of the microconstituents (42). If Kim’s argument for eliminativism about emergents because of reduction in principle goes through, a motivator of integrative pluralism is eliminated. In keeping with the pragmatic aspect of integrative pluralism, Mitchell’s assertion that complex systems have irreducible properties rests on the failings of explanatory reduction that necessitates descriptions. I was not convinced that explanatory emergence, associated with restricted epistemic access to information about actual microstructural dynamics, constitutes true ontological emergence. The ascribed novelty of explanatory emergence is about outcomes that are epistemically surprising due to observer limitations (42). Mitchell’s explanatory emergence does not establish actual physical emergents but simply applies the term ‘‘emergence’’ to refer to larger properties, objects or phenomena in a complex system that are unexpected or were unpredictable given significant epistemic access to information about the system. Mitchell’s treatment of explanatory emergence is nevertheless interesting and her exposition thereof non-trivial given the disputed status of emergence in philosophy. Chapter three proposes regarding generalisations in biology as laws by the pragmatic approach of determining whether a given generalisation in biology fulfils the functional role of scientific laws. This is part of the response to the limitations of static universalism and involves a typical pragmatic conceptual manoeuvre. Instead of debating whether biology has laws as they apply in physics or whether the laws of physics and biology are of a completely different kind, Mitchell calls for a new conception of laws which captures both the semantic overlap and the contrasts between laws in biology and physics (51). The greater universal applicability of the laws in fundamental physics, when compared to biology, is seen as simply a matter of the degree of contingency. The argument is that laws of physics, although usually more universal, are nevertheless ultimately either contingent or at least not logically necessary. I do not think it necessarily follows from the fact that generalisations about complex biological systems are demonstrably often contingent and contextual and that universal exceptionless laws are not possible. What is really at issue for Mitchell is representation and epistemic access to heterogeneous microstructure and interactions in complex (biological) systems. Integrative pluralism is partly a strategy for determining the right level(s) of abstractive explanation necessary for complex systems.
123
Metascience (2010) 19:441–444
443
Mitchell argues that the laws of physics are also contingent because of the scientist’s limited epistemic access to information about the world (55-6). Laws are taken to be contingent in an analogous way to that in which scientific theories are defeasible depending upon the reliable discovery of further facts. However, there is a distinction between a law as a representation of the natural world and regularities in it, and a natural law regarded as an actual objective regularity in the world. Mitchell differentiates them conceptually but then seems to collapse them together epistemically in the exposition to back her claim of necessary contingency for the laws of physics. In chapter four, Mitchell considers James Woodward’s conception of modularity for causal inference with complex systems. According to Woodward’s thesis individual causal mechanisms can be isolated within a more complex physical system. Causal inference-based analysis involves altering specific components or factors of the system and observing different effects on certain system properties in order to identify the altered component as causally linked to the given properties. For Mitchell, redundancy and robustness in complex biological systems undermine such analyses. Duplicates of isolated systems and effects that are multiply realisable by networks of interacting subsystems and features obscure causal links between modules and the function or property of interest. Different modules may contingently turn out to be highly interactive or interdependent such that they are not causally separable nor the mathematical equations that model them independently disruptable as required (77). Mitchell eschews redescribing the causal structure at a more detailed level to discern more causal mechanisms in the system. In that way, mathematical modularity may succeed, but it is a ‘‘make the world fit the theory’’ strategy impracticable for the study of complex systems in biology, where the explanatory objective is what has actually evolved. The preferred pragmatic integrative pluralist strategy requires the recognition of non-modular and other types of causality in nature. Modularity is seen as a form of causal reduction and thus as a case of reduction failing for complex systems. I think that Woodward’s method may not be so fragile, but Mitchell makes room for it in a pragmatic pluralist framework anyway. Chapter four closes with a call for a broader view of causal reality in philosophy and a corresponding pluralism in scientific approaches to causality (82). Chapter five promotes the idea of computer simulation and forecasting in robust adaptive planning as an alternative to predict-and-act models of scientifically informed policy making. Predict-and-act models establish a fixed policy and plan based upon a one-off statistical analysis and forecast models of the systems of interest, and thus fail to deal with deep uncertainty. Mitchell refers to the type of uncertainty inherent in complex non-linear and chaotic systems as deep uncertainty. Robust adaptive planning is promoted as the appropriate response. There is an evident epistemic and theoretic link between this and the idea of identifying complex systems as emergent on the basis that they require computer simulation for adequate analysis and modelling. This link is not foregrounded in Unsimple Truths. One of the significant strengths of integrative pluralism involves the imperative to render research and policy parallel undertakings in coping with the deep uncertainty that Mitchell attributes to complex systems.
123
444
Metascience (2010) 19:441–444
Many examples are provided in chapter six and throughout Unsimple Truths of how complex systems present difficulties to science and of putative examples of pluralist and integrative approaches in action. Unsimple Truths suggests a superior systematised way of approaching what Mitchell refers to as integrated multilevel explanation—the integration of information attained by investigating a given complex system at different levels of abstraction and organisation. However, integrative pluralism itself remains somewhat technically underspecified. It is presented as a set of largely consistent but general philosophical statements about the need to respond to complexity pragmatically and dynamically in a crossdisciplinary and contextual manner, coupled with endorsements of robust adaptive planning for overcoming deep uncertainty. I was thus unclear in the end of how superior integrative pluralism is to normative defeasible science enhanced by computer simulation and modelling. Nevertheless, in Unsimple Truths, the engagement with all associated issues is worthwhile, and it is executed in a thought-provoking manner.
123
