In spite of the heading, these approaches to nuclear structure physics are not in any contrast. They approach the problem of nuclear structure from opposite directions. We believe, however, that when many-body calculations will achieve their final goal, we will eventually understand why the simple shell model works so well and where it fails. The shell model has been used extensively and successfully for almost 60 years. It is still not understood why it is such a good approximation.

PACS numbers: 21.60Cs, 21.10.–k, 21.10.Pc