 In short, specialization is speciation, a scientific progress heightens communication breakdown. Experts doing similar kinds of research come to realize that their use of key taxonomic terms no longer jibes with mainline usage, in the sense that what Kuhn calls “the no overlap principle” is violated: the group is using a taxonomic hierarchy for crucial kind terms and the associated categories that is incompatible with that of the established tradition. The group splits off and forms a distinct specialty with its own professional journals, conferences, etc., while leaving the rest of the field largely intact. The incommensurability is now a local, community-licensed, taxonomic one that creates something of a barrier to communication with neighboring specialties. One thinks, for example, of the way different biological specialties employ the species concept itself, and the concept of gene. This linguistic sensitivity as a group identifier permits the kind of fullness of communication, both linguistic and practical, within the group that Kuhn had stressed already in Structure and thus permits the group to progress more rapidly. This multiplication of specialties is the key to Kuhn’s new conception of scientific progress. Two recent books that directly engage these issues are Andersen et al. (2006) and Wray (2011), the first from a cognitive science point of view, the second with emphasis on Kuhn’s social epistemology. See also Nersessian (2003, 2008) and Kuukkanen (2012).