Abstract
Theoretical biology and economics are remarkably similar in their reliance on mathematical models, which attempt to represent real world systems using many idealized assumptions. They are also similar in placing a great emphasis on derivational robustness of modeling results. Recently philosophers of biology and economics have argued that robustness analysis can be a method for confirmation of claims about causal mechanisms, despite the significant reliance of these models on patently false assumptions. We argue that the power of robustness analysis has been greatly exaggerated. It is best regarded as a method of discovery rather than confirmation.
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Notes
Robustness analysis is often used by scientific realists to argue for particular claims being true or certain entities as existing and bears a passing resemblance to the “no miracle argument”. However, generally, robustness analysis is different than the no miracles argument. Robustness concerns the following conditional probability, Pr(O/M 1&M 2&···&M n ), and the no miracles argument concerns the following conditional probability, Pr(M/O 1&O 2&···&O n ). where O i are predictions and M i are models (or theories).
It is not clear that these types of assumptions are that different. For example, a causal assumption that some factor C causes E assumes certain intervening factors are absent. But we leave worries like these to the side.
Suppose Pr(O/C&A 1) ≠ Pr(O/C&A 2) where O is some prediction, C is the common “substantial” core, and the A i s are different idealized assumptions. It follows that [Pr(O)Pr(C&A 1/O)]/Pr(C&A 1) ≠ [Pr(O)Pr(C&A 2/O)]/Pr(C&A 2). Thus, Pr(C&A 1) ≠ Pr(C&A 2). However, this is consistent with Pr(A 1/A 2) ≠ Pr(A 1).
Our views should not be construed as skepticism regarding causal claims. For example, we have reason to believe the Volterra Principle is a true causal claim when we can intervene in a predator–prey system and produce the intended effect. For example, all things being equal, if we instantiate the antecedent and the consequent is observed that is reason to believe the Volterra Principle describes a causal relationship. However, if we do this, robustness analysis plays no role in confirmation.
A common response to this sort of argument is that we employ a notion of approximate truth and suggest that say A j is closer to the truth than A i . However, as far as we are aware, no such account of approximate truth is successful. And in any case, many of the false assumptions in question are not even close to truth on any understanding of approximate truth.
Julian Reiss has recently made this point forcefully for economics (Reiss 2008 118–119).
That is, given his prior probability with regard to those idealizations was zero, then regardless of the likelihoods, the posterior probability must be zero.
There is also a tradition in the semantic view of theories for regarding models as providing theoretical “definitions” or set-theoretical predicates. Thus, syntactically or semantically, we can separate the model from the model’s application.
This implies that we also reject the view that models state capacity claims (Cartwright 1999) or make claims about credible worlds (Sugden 2000, 2009). For reasons to reject these views see Cartwright (2009), Gruene-Yanoff (2009), Alexandrova (2008), Alexandrova and Northcott (2009), and Odenbaugh (2006).
See Al Roth, the father of design economics (among many others, of course) on the complex mixture of methods that goes into successful applied economics (Roth 2002).
“Natural experiments” are important in both economics and biology. Here one finds to situations such that some purported causal factor is present in the former and not the latter and where everything else is roughly the same. The problem with these so-called experiments is that rarely are they even roughly the same. Still, they can be important.
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Acknowledgments
Authors would like to thank Michael Weisberg, Robert Northcott, Nancy Cartwright, Uskali Maki and two anonymous referees for useful comments on the paper.
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Odenbaugh, J., Alexandrova, A. Buyer beware: robustness analyses in economics and biology. Biol Philos 26, 757–771 (2011). https://doi.org/10.1007/s10539-011-9278-y
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DOI: https://doi.org/10.1007/s10539-011-9278-y