We discuss supergravity from an S-matrix point of view. Kinematical constraints on helicity amplitudes determine the spin-2 and spin-3/2 Born amplitudes almost uniquely, and force Born amplitudes involving spin-5/2 fermions to vanish. Global supersymmetry is then used to determine the Born amplitudes completely. We suggest that Lorentz invariance, presence of only one (dimensional) coupling constant κ, and global supersymmetry lead to a unique locally supergauge-invariant theory of spin-2 and spin-3/2 particles. We draw similar conclusions for a model uniting supergravity and the Wess-Zumino scalar multiplet.