 A lexicon is not only prerequisite to making meaningful statements, it also sets limits on what can be meaningfully said within the community of speakers that share it: “There is, for example, no way, even in an enriched Newtonian vocabulary, to convey the Aristotelian propositions regularly misconstrued as asserting the proportionality of force and motion or the impossibility of a void. Using our conceptual lexicon, these Aristotelian propositions cannot be expressed — they are simply ineffable — and we are barred by the no-overlap principle from access to the concepts required to express them ” (Kuhn 2000 [1993], 244; cf. 2000 [1989], 76). In this way, Kuhn’s later notion of the incommensurability of scientific theories is based on effability. The structure of the lexicon shared by a particular community determines how the world can be described by its members, as well as how they will misunderstand the history of their own discipline; that is, unless they learn to understand older terms according to the structure of the older lexicon. Where Kuhn had earlier likened the process by which historians come to understand antiquated science as a special type of translation, he retracted these claims, insisting that the process is one of language learning, not translation (2000 [1993], 238, 244). Kuhn often claimed that incommensurable theories are untranslatable (e.g. Kuhn 2000 [1991], 94). However, he also emphasized that translation is neither needed in the comparison of incommensurable theories, nor in the hermeneutic historical method necessary to understand antiquated sciences (Kuhn 2000 [1993], 237, 238, 244). To overcome the barriers posed by incommensurability to understanding antiquated sciences, and to understanding the special technical vocabulary used by contemporaneous, phylogenetically related sub-disciplines, it is neither necessary not possible to translate between them. Rather, one must become bilingual, learning to use (and keep separate) the incongruently structured lexical taxonomies underwriting different laws and theories.