  We study Translation functors and Wall-Crossing functors on infinite
dimensional representations of a complex semisimple Lie algebra using
D-modules. This functorial machinery is then used to prove the
Endomorphism-theorem and the Structure-theorem, two important results
established earlier by W. Soergel in a totally different way. Other
applications to the category O of Bernstein-Gelfand-Gelfand are given, and some
conjectural relationships between Koszul duality, Verdier duality and
convolution functors are discussed. A geometric interpretation of tilting
modules is given.
