  Anomalies can be viewed as arising from the cohomology of the Lie algebra of
the group of gauge transformations and also from the topological cohomology of
the group of connections modulo gauge transformations. We show how these two
approaches are unified by the transgression map. We discuss the geometry behind
the current commutator anomaly and the Faddeev- Mickelsson anomaly using the
recent notion of a gerbe. Some anomalies (notably 3-cocycles) do not have such
a geometric origin. We discuss one example and a conjecture on how these may be
related to geometric anomalies.
