Yes -- Tink I am soon going to resume Saul's book, I think. The parts I was understanding seemed very powerful, but I could not really 'get it,' the whole point he was trying to build. I think the book came out 1992, but so much of what I was understanding is valid today, very current.
"But it seems to me that acting on false premises is hardly a use of reason, nor does it validate nefarious motives, it simply advances them. "
This may be his whole message, that since Voltaire we have been misusing/abusing the gift of reason, even while claiming (falsely) its enlightenment. That dovetails with another book I found very useful, came out in the 1950's and was a watershed for explaining existentialism to Americans. I may read it again -- that author (William Barrett) seemed to be saying that right up until the 1914 assassination in Sarajevo, the empires seemed to have the world so well-ordered, under tight control, based (they thought) on the Age of Reason -- and then a few months later WWI exploded.
And as you already know, all this is of very special interest to me because I think it is important to comprehend as much as possible our present world and national conundrum, recently all exacerbated by coronavirus!
Lessee...you are ~40, which means Grandmother could hardly be younger than 80, probably older since she has understanding of Weimar and Third Reich -- certainly a treasure for you and the whole world...is she still with us?