The best reply I can give to the question Lionel regarding 
exception and hypothetical refers to Lumen Gentium and
 Cardinal Muller. Insofar as logical sequence an 
exception may be attributed to a hypothetical. Your
 argument that the hypothetical, which is only a
 possible cannot confirm an exception to no salvation 
outside the Church. There is no means of confirming
 the hypothetical as a reality. That may be true insofar
 as actual persons since only God would know. 
Nonetheless conscience is inviolable. To follow 
conscience is akin to obeying God. The condition to
 that however is there are some things we should
 know. The only exception would be invincible
 ignorance, meaning that the knowledge in question 
is not possible for the individual to know. Based on
 this explanation given by Saint Thomas Aquinas
 in the Summa, which i hold as correct we have to
 assume, hypothesize there may be persons who
 are invincibly ignorant of Christ's revelation. So 
the teaching extra ecclesiam nulla salus may 
reasonably be understood as requiring knowledge
 of Christ's revelation. If it were understood as 
an absolute sans exception you would be correct. 
The Church however has the authority to interpret 
and teach its doctrines, which are not subject to 
opinion. Faith in Christ and his Church is a mandate.

Fr. Peter Morello, Ph.D.
The best reply I can give to the question Lionel
regarding exception and hypothetical refers to
Lumen Gentium and Cardinal Muller. Insofar
as logical sequence an exception may be
attributed to a hypothetical.