 Kuhn continued to struggle with, develop, and then refine his understanding of incommensurability until his death in 1996. Although his development of incommensurability went through several stages (cf. Hoyningen-Huene 1993, 206-222), he claimed to have made a “series of significant breakthroughs” beginning in 1987 (Kuhn 2000 [1993], 228). They are described in a number of essays and published lectures that were collected in (Kuhn 2000, cf. chs. 3, 4, 5, 10 &amp; 11), and a last as yet unpublished book by Kuhn on incommensurability is still pending (Conant and Haugeland 2000, 2). The nature of these developments is controversial. Some commentators claim that Kuhn’s incommensurability thesis underwent a ‘major transformation’ (Sankey 1993), while others (including Kuhn himself) see only a more specific characterization of the original core insight (Hoyningen-Huene 1993, 212; Kuhn 2000, [1983], 33ff.; Chen 1997). Kuhn’s original holistic characterization of incommensurability has been distinguished into two separate theses. ‘Taxonomic incommensurability’ involves conceptual change in contrast to ‘methodological incommensurability’, which involves the epistemic values used to evaluate theories (Sankey 1991; Sankey and Hoyningen-Huene 2001; see Section 2.3.2 below).