This book originated in the Workshop on "Hadronic Matter at Extreme
Energy Density," held at the Ettore Majorana Center in Erice, October
13-21, 1978. The lectures have been expanded to their present size, and
the contributions of seven seminars have been represented by abstracts
which should stimulate the reader's interest and guide him to the
original literature. The title of the book perhaps does not fully
represent its content but still is a good indication of the conceptual
motiva- tion of our Workshop. The development of physics in recent years
has filled in the first details of the grand design which was initiated
with the theory of general relativity and aspires to a synthesis of all
the different interactions. However, this development has not been a
linear one but .has followed a divided pattern: general relativity had
its phenomenological domain in cosmology and had little to do with
high-energy elementary particle physics. It was progress in the
knowledge of symmetries in particle physics that fueled the advance
toward the present formulation of supergravity, thus help- ing to heal
this historical separation. The great program would not have advanced so
far if our attention had all the time stayed focused at infinity, where
the great issues are.