A CLASSICAL APPROACH TO HIGHER DERIVATIVE GRAVITY

Two classical routes towards higher-derivative gravity theory are de- scribed. The first one is a geometrical route, starting from first principies. The second route is a formal one. and is based on a recent theorem by Castagnino et a). (J.Math.Phys. 28 1854 (1987)). A cosmological solution of the higher- derivative field equations is exhibited. which in a classical framework singles out this gravitation theory.