Christian iconography and its visual vocabulary derive fromg both the allegorical language used by Christ himself, as well as the need for covert symbols in Christianity's underground days prior to Constantine...
We also forget that medieval art was not perceived as “reporting,” but was highly symbolic. Figures weren’t just themselves but represented something else. Furthermore, the spectators knew what they represented; that is, they could read these symbols.
For example, early Nativity scenes (post St Francis, at least) always had a certain set of figures, among which were the Ox and the Ass. Naturally, anybody looking at it knew that the Ox and the Ass represented the Gentiles and the Jews, just as the Three Kings represented the “three races of man,” and were shown as being of different ages because they represented the “ages of man.” So visual works and even folk representations were laden with doctrinal content.
This, of course, is one of the reasons that visual representations were a major target of the so-called reformers.
Christian iconography and its visual vocabulary derive fromg both the allegorical language used by Christ himself, as well as the need for covert symbols in Christianity's underground days prior to Constantine...
Not exactly. "An ox knows its owner, and an ass, its master's manger; But Israel does not know, my people has not understood." Isaiah 1:3
Indeed. This is why when Molanus says
‘Many painters show Mary and John the Baptist kneeling beside Our lord at the Last Judgment...But we may not think that at that day the Virgin Mary will kneel for us before the Judge, baring her breast to intercede for sinners. Nor may we think that John the Baptist will fall upon his knees to beg mercy for mankind in the way the painters show. Rather, the blessed Virgin and St. John shall sit beside the supreme Judge as assessors. The mercy which is extended now will have no place then. There will only be strict justice at that day.’, he may be making a theological point -- all wrong, like his entire Protestant theological jumble -- but his point, such as it is, has nothing to do with what is and what is not a valid artistic expression of the Last Judgement.
In the Eastern Byzantine tradition one won't see Our Lady baring her breast, but one will see her and St. John the Baptist pleading for divine mercy, because that is the faith of our fathers East and West.
It just makes sense as there were few books and few readers of books. It also makes sense that the Church used all the senses, I don’t think it was coincidence.