Everything that exists in the world of Nefesh (individual souls)
exists also in the worlds of shana (time) and olam (space/place).
Many things that used to be permitted because the Torah allowed them
have become forbidden since matan Torah through various takanos and
gezeiros miderabbanan, rabbinic decrees.
Every posek or opinion in Chazal speaks and paskens according to the
root source of that person's soul, and this is the ratzon Hashem
because He created those people from their own specific source for a
Reason and caused the rules of psak to accomodate a wide variety of
Therefore those piskei halacha rooted in the world of nefesh of those
poskim/divrei Chazal, found their expression in those places (Olam)
and times in history (shana) to which they were appropriate.
Because the generations have decreased in holiness and purity since
Creation,and because permittedness (koach d'heteira) is rooted in
purity/holiness and forbiddenness is rooted in tumah/impurity, as the
world has descended to greater impurity, the power of forbiddenness
has increased, as we have seen.
This is obviously G-d's will because it is the product of His
infinitely exact providence.
One question I have on these ideas is whether the author means that
forbiddenness is itself an expression of the koach of impurity that
has increased or whether he means that strictness/forbiddenness is
merely the correct response to the existance of the greater presence