  If inflation is to be considered in an unbiased way, as possibly originating
from one of a wide range of underlying theories, then observations need not be
simply applied to reconstructing the inflaton potential, V(\phi), or a specific
kinetic term, as in DBI inflation, but rather to reconstruct the inflationary
action in its entirety. We discuss the constraints that can be placed on a
general single field action from measurements of the primordial scalar and
tensor fluctuation power spectra and non-Gaussianities. We also present the
flow equation formalism for reconstructing a general inflationary Lagrangian,
L(X,\phi), with X={1/2}\partial_\mu\phi\partial^\mu\phi, in a general gauge,
that reduces to canonical and DBI inflation in the specific gauge \partial
L/\partial X = c_s^{-1}.
