.
One of Rome's earliest official proclamations regarding a Purgatory was Pope
Leo X's Bull of Exsurge Domine. In the year 1520 AD he stated, along with
some other things, that death is the termination not of nature but of sin, and
this inability to sin makes [purgatorial souls] secure of final happiness; viz:
according to Leo X's proclamation, the occupants of a Purgatory are 100%
sinless.
It's not too difficult to appreciate just how essential it would be for souls in
a Purgatory to be incapable of sinning, because if they weren't, then Rome’s
promise in CCC.1030, of an assured eternal salvation for purgatorians,
would be a tenuous guarantee indeed since each new sin committed while
interred in a Purgatory would add time to the penitent’s original sentence;
with the very real possibility of potentially snow-balling to the point where
they would never be released.
_