Lardiere's keynote article adverts to a succession of `units of comparison' that have been employed in the study of cross-linguistic differences, including mid-twentieth-century structural patterns, generative grammar's parameters, and (within contemporary Minimalism) features. This commentary expands on the idea of units of cross-linguistic comparison, first by developing Lardiere's observations about recent scholarship and, second, by identifying some earlier reflexes of the notion. I close by suggesting that thinking about `units of comparison' across time prepares us to better appreciate a feature-based conceptualization of L2 acquisition, and its likely trajectory.
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