  The common assumption that Theta-1-Ori C is the dominant ionizing source for
the Orion Nebula is critically examined. This assumption underlies much of the
existing analysis of the nebula. In this paper we establish through comparison
of the relative strengths of emission lines with expectations from Cloudy
models and through the direction of the bright edges of proplyds that
Theta-2-Ori-A, which lies beyond the Bright Bar, also plays an important role.
Theta-1-Ori-C does dominate ionization in the inner part of the Orion Nebula,
but outside of the Bright Bar as far as the southeast boundary of the Extended
Orion Nebula, Theta-2-Ori-A is the dominant source. In addition to identifying
the ionizing star in sample regions, we were able to locate those portions of
the nebula in 3-D. This analysis illustrates the power of MUSE spectral imaging
observations in identifying sources of ionization in extended regions.
