The author defended his doctoral thesis on the concept of Ignatius' zeta omega eta in 1975, and published it in 1977. Now he reviews the literature since then, noting some aspects that call attention this. Afterwards, he presents his thesis and finishes with a condensed conclusive synthesis. The author does not stop here to consider at any length the recent authors who deny the authenticity of the middle version, leaving them for a complementary article, in order not to unduly lengthen this present article.