It is generally thought that Carnap’s principle of tolerance cannot be integrated into a coherent overall conception of rationality. The doubts come from many sides, of which two are singled out. This paper argues that both are wrong, and that Carnapian rationality is a viable and perhaps quite interesting program for further development.

Huw Price has sketched a program for a globalized expressivism in support of which he has repeatedly invoked Rudolf Carnap. This paper argues that this is entirely appropriate, as Carnap had something quite similar in mind. However, it also argues that Price’s recent attempts to integrate Robert Brandom’s inferentialism to this program are less successful, and that a more empirically-oriented descriptive pragmatics along Carnapian lines would be a better fit with his original program than Brandom’s explicitly hermeneutical agenda.

Whereas there is much discussion about Thomas Kuhn’s notion of methodological incommensurability and many have seen his ideas as an attempt to allow for rational disagreement in science, so far no serious analysis of how exactly Kuhn aims to account for rational disagreement has been proposed. This paper provides the first in-depth analysis of Kuhn’s account of rational disagreement in science—an account that can be seen as the most prominent attempt to allow for rational disagreement in science. Three things will (...) be shown: First, we find not one, but two accounts of rational disagreements in science in Kuhn’s writings: one stemming from methodological incommensurability and one stemming from Kuhn-underdetermination, which are not only fundamentally different—the first purports to explain how disagreeing scientists can nevertheless be rational, while the second attempts to show how rational scientists can nevertheless disagree—but appear to be incompatible with each other. Second, I will assess both accounts. Kuhn’s account from methodological incommensurability is not convincing since it cannot explain rational disagreement in science. Whereas, on the other hand, Kuhn’s account from Kuhn-underdetermination allows for rational disagreement, his argument why we should accept it is not convincing. Third, I present a tentative sketch of an alternative to Kuhn’s account that emphasizes the fallibility of epistemic justification in order to show that Kuhn’s argument founders. In sum, the paper shows that focusing not on the muchly debated consequences of methodological incommensurability, but on Kuhn’s treatment of rational disagreement gives new insight into the adequate interpretation of his thought as well as the cogency of his ideas. (shrink)