  Most nuclear physics ranges from insensitive to relatively insensitive to
many-nucleon forces. The dominant ingredient in calculations of nuclear
properties is the nucleon-nucleon potential. Three-nucleon forces nevertheless
play an important role in nuclear physics because of the great precision of
modern calculational methods for systems of relatively few nucleons. We explore
the reasons why many-body forces are weak in nuclei by using a classification
scheme for such forces that is based on dimensional power counting, which is
used to organize chiral perturbation theory. An assessment will be made of how
close we are to a ``standard'' three-nucleon force. Recent advances in
determining the significance of three-nucleon forces will also be discussed.
