This will sound strange but I studied under R. Parnes, and I'm
acquainted with Dr. Shapiro. I don't know R. Leff but I did read his
As I see it [aisi], they are not so much arguing as talking past each
other. R Parnes and R Leff are asserting a generality that all
Observant Jews have come to accept the "13 Principles" Dr. Shapiro
argues that the 13 Principles as specifically articulated by the Rambam
has been quibbled with for centuries.
IMHO - both sides are essentially correct.
The acceptance of the 13 may be summarized - for example - By Yigdal.
Everyone seems to accept these in principle. The original version as
articulated by the Rambam was - as I understand it - never accepted by
everyone without at least some objections.
To Reject the 13 as understood EG by R Parnes would indeed be beyond
the pale. To reject the very specific formulation of Rambam and quibble
about P'rattim would probably be quite acceptable. EG Anyone who
recites Machinsei Rachamim or Borchuni L'shalom is rejecting the strict
construction of the Rambam's formulation. Rather, those who recite
these have a looser construction of the 13, one that in Yeshivishe
Circles would not be deemed a "rejection".