This paper examines the cognitive platform for rational comparison between rival theories.Arguments are developed by drawing on the results of cognitive psychology,which reveals the cognitive mechanisms behind the practice of concept representation and taxonomy construction.The taxonomic change in 19th?century ornithology is also used to uncover the historical practice that scientists employed in the revision of the classification of birds.On the basis of cognitive and historical analyses,I argue that sameness in global and holistic lexical structures,such as taxonomies, which is not the merely platform for rational comparison between rival theories.During taxonomic changes,rational comparisons between incommensurable theories can be performed on “platforms’ that are neither global nor lexical.detailed analyses show that rational comparisons were achieved in the historical case through sharing local lexical structures, such as compatible contrast sets,as well as non?lexical structures, such as compatible partonomies.
