ELFE: An electron laboratory for europe Original Research Article

After about 10 years of discussions the physics case for ELFE, the Electron Laboratory For Europe, has become much clearer. The paper gives a personal view of the salient physics visible today. It is argued that QCD cannot be taken as the the “theory of strong interactions” as long as it cannot describe the hadronic world at low energies. New theoretical tools as “semi-exclusive reactions” and “off-forward-parton distributions” are promising new insight into hadrons by means of new observables. It is shown how connection of the new observables to QCD can be made. The most important parameters for an ELFE following from these conjectures are given allowing an experimental study of this physics.