  Recently Penrose, Sorkin and Woolgar have developed a new technique for
proving the positive mass theorem in general relativity. We extend their result
to produce a new inequality relating the mass, electric and scalar charges in
theories coupling to a dilaton in the usual way. Using a five dimensional
formalism, our result provides new information not available from the existing
techniques. The main result may be simply expressed as
  M + g\Sigma \ge { \sqrt{1+g^2} |Q| \over \sqrt {4\pi G} } . where `M' is the
A.D.M. mass, `Q' is the electric charge, `\Sigma' the scalar charge and `g' is
the dilaton coupling parameter.
