Strings from Almost Nothing

We argue that string theory emerges inevitably from a few simple assumptions about physical scattering. Consistency alone requires that all tree-level four-point scattering amplitudes exhibit vanishing residues at prescribed values of the momentum transfer. Assuming ultrasoft high-energy behavior, we then prove that the space of minimally consistent amplitudes, whose residues exhibit these mandated zeros and nothing more, are precisely the amplitudes of Veneziano and Virasoro-Shapiro, thus establishing the uniqueness of strings. Similar logic also applies to five-point scattering.