  To understand the physical conditions of various gaseous systems, plasma
diagnostics must be performed properly. To that end, it is equally important to
have extinction correction performed properly. This means that the physical
conditions of the target sources -- the very quantities to be derived via
plasma diagnostics -- must be known even before performing extinction
correction, because the degree of extinction is usually determined by comparing
the observed spectra of the target sources with their theoretically predicted
counterparts. One way to resolve this conundrum is to perform both extinction
correction and plasma diagnostics together by iteratively seeking a converged
solution. In fact, if these analyses are performed self-consistently, a
converged solution can be found based solely on well-calibrated line
intensities, given the adopted extinction law and the R_V value. However, it is
still rare to find these analyses done numerically rigorously from start to
finish. In this contribution for the APN 8e conference, we would like to review
this convoluted problem and sort out critical issues based on the results of
our recent experiments. It appears that the convoluted theoretical and
observational progresses exacerbated by the highly numerical nature of these
analyses necessitated a number of analytical simplifications to make the
problem analytically tractable in the pre-computer era and that such analytical
simplifications still remain rampant in the literature today even after ample
computational resources became readily available. Hence, the community is
encouraged to do away with this old habit of sidestepping numerical
calculations, which may have been a necessary evil in the past. This is
especially true in the context of spatially-resolved 2-D spectroscopy, which
obviously conflicts with the uniformity assumption often blindly inherited from
1-D spectroscopy.
