  We derive a universal soft theorem for every scattering amplitude with at
least one massless particle in an arbitrary theory of scalars. Our results
follow from the geometry of field space and are valid for any choice of mass
spectrum, potential terms, and higher-derivative interactions. For a vanishing
potential, the soft limit of every amplitude is equal to the field-space
covariant derivative of an amplitude with one fewer particle. Furthermore, the
Adler zero and the dilaton soft theorem are special cases of our results. We
also discuss more exotic scenarios in which the soft limit is non-trivial but
still universal. Last but not least, we derive new theorems for multiple-soft
limits which directly probe the field-space curvature, as well as on-shell
recursion relations applicable to two-derivative scalar field theories
exhibiting no symmetries whatsoever.
