Not to say

[Se�n Fitzpatrick]

Here's an idiom question.  
I started to write "the Catholic, not to say Christian, doctrine" and realized I am not sure which way NtS swings.  What is the import of the somewhat UKish expression "not to say", as in "A, not to say B..."?  Is it different from the neutral "not to mention"?
  1.. Inclusive aside; "not to mention", "my argument could be even stronger", e.g., "the Christian, not to say legal, prohibition" 
  2.. Intensification; "a fortiori"; e.g., "the Christian, not to say Catholic, doctrine" 
  3.. Categorical inclusion; "it goes without saying"; e.g., "the Christian, not to say Catholic, doctrine" 
  4.. Categorical expansion; "I am speaking more narrowly than I need to; e.g., "the Catholic, not to say Christian, doctrine"

Seán Fitzpatrick
Does "Thou shalt not steal", etc. on the courthouse create a hostile environment for lawyers and politicians?
http://www.logomachon.blogspot.com/