  We argue that from the point of view of gauge theory and of an appropriate
interpretation of the interferometer experiments with matter waves in a
gravitational field, the Einstein-Cartan theory is the best theory of gravity
available. Alternative viable theories are general relativity and a certain
teleparallelism model. Objections of Ohanian and Ruffini against the
Einstein-Cartan theory are discussed. Subsequently we list the papers which
were read at the `Alternative 4D Session' and try to order them, at least
partially, in the light of the structures discussed.
