This chapter examines Kuhn’s later work on incommensurability in terms of his rational reconstruction of scientific theories in terms of structured taxonomies of kind terms, and the concomitant effect it had on his picture of scientific revolutions. We also examine Kuhn’s later analogy of the proliferation of scientific specialties with biological speciation; on Kuhn’s later view, a revolution did not always result in the replacement of one theory with another – sometimes a new scientific specialty broke off from the parent branch.