  The simplest higher-spin interactions involve classical external currents and
symmetric tensors $\phi_{\m_1 ... \m_s}$, and convey three instructive lessons.
The first is a general form of the van Dam-Veltman-Zakharov discontinuity in
flat space for this class of fields. The second is the rationale for its
disappearance in (A)dS spaces. Finally, the third is a glimpse into an option
which is commonly overlooked in Field Theory, and which both higher spins and
String Theory are confronting us with: one can well allow in the Lagrangians
non-local terms that do not spoil the local nature of physical quantities.
