  We review various derivations of the partition function of the
two-dimensional Ising Model of ferromagnetism and proofs of the stability of
matter, paying attention to passages where there would appear to be a lacuna
between steps or where the structure of the argument is not so straightforward.
Authors cannot include all the intermediate steps, but sometimes most readers
and especially students will be mystified by such a transition. Moreover,
careful consideration of such lacunae points to interesting physics and not
only mathematical technology. Also, when reading the original papers, the
structure of the physics argument may be buried by the technical moves.
Improvements in the derivations, in subsequent papers by others, may well be
clearer and more motivated. But, there is remarkably little written and
published about how to read some of the original papers, and the subsequent
ones, yet students and their teachers would often benefit from such guidance. I
should note that much of the discussion below will benefit from having those
papers in front of you.
