The Idealized Mind (2025) examines how idealized models are used to interpret the nature and function of the mind and brain, whilst defending a version of scientific realism.
Drayson presents several challenges to this project. She says that The Idealized Mind claims that “some scientific theories are neither true nor false” and that this makes me “one of the very few philosophers since the logical empiricists to deny semantic realism.” That’s a misreading of the book’s position. My worry about semantic realism – the view that scientific discourse is truth-conditional – only concerns idealization. I defend the view that most scientific models consist of mixed components: (i) idealized parts, serving no representational function across the model-world relation; and (ii) nonidealized parts, which may represent (in various ways) aspects of the target system (see e.g., p. 61, pp. 68-69). There is no logical empiricism here. To suggest otherwise, would be to examine a straw version of the book’s main arguments.
Drayson worries about my nonliteral view of idealization (chapters 3-4): “how could we use the model to reason about the roles played by aspects of the target system unless the model also performed some sort of representational function with respect to the target system?” There’s no need to worry. Consider the Hardy-Weinberg model. It shows that in the absence of evolutionary forces, allele frequencies remain constant over generations. It is based on five idealizations: (a) zero mutation; (b) zero gene flow; (c) no natural selection; and (d) random mating. These idealizations make it the case that allele frequencies remain constant over generations in virtue of a crucial fifth idealization: (e) a biological population must be infinitely large. The idealizations are useful because they define a baseline ideal world in which allele frequencies do not change. The infinity function, I argue in the book, does not misrepresent biological populations as infinite. It is not useful, as many think, in virtue of being false. The infinity idealization is a mathematical tool that does one thing: it eliminates stochastic effects that occur in finite populations. The useful implication of this is: a clean baseline null model, i.e., any deviation from the deterministic mapping ‘allele frequency ® genotypic frequencies’, guaranteed by the infinity function, must be due to non-random mating, selection, population structure, etc. I argue that idealizations must be treated nonliterally, i.e., as lacking truth-values over the model-world relation. Yet, Drayson questions, how can one reason with such a model? I’ve just given you one example. Here’s a second one. One can make use of idealizations as the antecedent structures of a conditional to make inferences to measurable consequences about allele frequencies. This is what I argue in chapter 9 of The Idealized Mind, although in a discussion of the free energy principle in theoretical neuroscience.
Finally, Drayson worries that a nonliteral treatment of idealization makes scientific discourse meaningless, jeopardizing any defence of scientific realism. It is entirely possible to relax the semantic thesis of scientific realism without weakening a defence of scientific realism. Moreover, the insistence on scientific representation is unnecessary. Idealized models often look nothing like their targets.
References
Kirchhoff, Michael. 2025. The Idealized Mind: From Model-based Science to Cognitive Science. Cambridge, MA: The MIT Press.