 Even so, Fleck emphasized all three of the interrelated aspects of the shifts that Kuhn called revolutions and tried to capture by calling theories ‘incommensurable’ (changes in problems and standards (1979 [1935], 75–76; 1979 [1936], 89), conceptual change (e.g. 1979 [1935]; 1979 [1936], 72, 83) and world change (e.g. 1986 [1936], 112). Fleck argued that science does not approach the truth because successive thought-styles raise new problems and discard older forms of knowledge (Fleck 1986 [1936], 111–112; 1979 [1935], 19, 51, 137–139; cf. Harwood 1986, 177). Fleck emphasized that scientific terms acquire their meanings through their application within a particular theoretical context and that those meanings change when theories change in the course of advance, even offering the example of ‘chemical elements’ and ‘compounds’ repeated by Kuhn (Fleck 1979 [1935], 25, 39, 40, 53–54). Fleck emphasized the theory-ladenness of observation with explicit reference to Gestalt switches; stressing that a ‘thought-style’ determines not only the meanings of the concepts it uses, but also the perception of phenomena to be explained, developing examples from the history of anatomical representation (1979 [1935], 66; 1986 [1947]). Fleck (like Kuhn, Feyerabend and Wittgenstein) acknowledged Wolfgang Köhler’s work in psychology of perception in this regard. Fleck concluded that scientific advance is not cumulative, that conceptual differences between members of different scientific communities cause communication difficulties between them (1979 [1936], 109), and later for historians trying to understand older ideas (1979 [1936], 83–85, 89). Fleck even emphasized that meaning change in the course of scientific advance causes translation failure between theories, anticipating a central aspect of Kuhn’s later notion of taxonomic incommensurability (e.g. 1986 [1936], 83).