Oblique predicative constructions in English with for and as: qua vs qualitate qua

English has an oblique predicative construction in which the prepositions for and as license an oblique predicative complement that is predicated of a noun phrase, as in We took her for a friend and I regarded her as a genius . The construction with for is the oldest, and is found in many other languages. This article traces the history of oblique predicative constructions involving for and as , and a number of other prepositions, from Old English to Present-Day English (PDE). Visser (1963–73) has suggested that predicative for and as were rivals, and that in PDE as is now dominant at the expense of for . I will argue instead that since around 1900 predicative for and as can clearly be distinguished semantically as expressing the meanings qua (‘as being’) and qualitate qua (‘in the capacity of’), respectively, and that the existence of these distinct meanings explains why constructions with both prepositions still survive in PDE.