A principles and parameters account of the Case marking properties of the Turkish postposition için and its cognates in other Turkish languages

The Turkish word için 'for' acts in a complex manner in terms of the Cases which it assigns to its complements. The equivalent words in some other languages of the Turkic family, both modern and older, also have a complicated behavior and/or differ from için in this respect. I propose an account for this set of facts which makes use of posited changes in the categorial features of these words, and which connects structural Case marking to different feature values than is standardly assumed.