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In his new book (From empiricism to expressivism: Brandom reads Sellars, Harvard University Press, Cambridge, 2015), Brandom offers a new argument against the viability of Sellars’ scientific naturalism. Brandom attempts to show that if the Sellarsian it scientia mensura principle is understood as implying that manifest-image objects exist only if they are identical to scientific-image objects, it is undermined by the ‘Kant–Sellars’ thesis about identity which implies that manifest-image objects cannot be identical to scientific-image objects. This conclusion can be evaded by construing the relation between manifest and scientific objects as weaker than that of identity, namely as a relation between manifest-image functional roles and scientific-image realizers. But Brandom again argues that even this weaker construal of the scientia mensura thesis is in conflict with another Sellarsian argument, this time against phenomenalism. It will be argued that this is not so. I will, moreover, suggest that the ‘function-realizer’ construal of the manifest-scientific image distinction is indeed tenable—especially if the process of determining the scientific-image realizers of functional roles specified in manifest-image is understood as the culmination of a self-correcting dynamic and diachronic process of conceptual change. Finally, I will argue that while Brandom is right to point out that Sellars’ adherence to the scientia mensura principle is based on a ‘unity-of-science’ view, he is wrong to think that his argument for the contrary conclusion (the ‘disunity-of-science’ view) is successful, because Brandom’s argument does not automatically tell against a weaker ‘unity-of-science’ view according to which incommensurability of explanatory levels in science is a pragmatically indispensable yet in principle dispensable feature of empirical inquiry.

DOI: 10.1007/s11229-016-1271-1

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