I am looking for a good article to post on this subject, primarily because we have a reader who seems eager to address the issue. Any suggestions?
I see Catholicism.org has a whole list of linked articles on the issue; Farley Clinton has an article entitled "The Leonard Feeney Quarrel and Pius IX on Invincible Ignorance" (CatholicCulture.org) that is fairly lengthy. Googling "Feeney" and "invincible ignorance" brings up an SSPX article roundly criticizing Fr. Feeney's book, The Bread of Life (1952) as contradicting Church teaching. Here are some more historical details concerning Abp Cushing and the Holy Office from EWTN. The bottom line, as far as I can see, has to do with how "Extra ecclesiam nulla salus" is meant to be understood. Feeney (excommunicated in 1953) apparently held that original sin is wiped away only by the character imprinted on the soul by Baptism. Does this mean nobody under the Old Covenant (Abraham, Isaac, Jacob, Moses) is to be found among the saved? Absurd. So then, what does the statement mean? Have at it, if any of you are interested. Only, please observe the rules of common sense etiquette. Stick to the subject. No ad hominems or rudeness. No "carpet bombing" of copied text into the combox. No unwarranted inferences from cited sources casting aspersion on anyone. Etc. Etc. Etc.
Related: Geertjan Zuidwegt, "Salvation and the Church: Feeney, Fenton, and the Making of Lumen Gentium" (Academia.edu, Louvain Studies, 37 , 147-178)