If someone is speaking about a current idea, there is no dis-congruity since the underlying premise is still widely known in society. (A/A) However as time changes the underlying premise of understanding changes on a number of levels. As the meaning of words change based on common use, this can cause misunderstandings, but people who still remember "how it was" because "they were there" it's not as difficult. However, since the young generation would actually need to take the older generation's word for it, there is still something lost in the explanation. (A/B)
As a century or two pass, no one remembers what premise A or B was all about, and only have recording of Idea A. (A/C)
Some more time passes and an event that is considered a societal tragedy occurs and becomes part of the underlying premise of understanding. This results in a logic where the original idea still exists, but the current premise cannot accurately translate what that meant anymore ... since things are different now. (A/Aa)
Since a number of tragedies and revolutionary events occurred over time and changed the way people perceive ideas, saying A/A is no longer possible, since the underlying premise is Rz. (A/Rz)
However, sometimes things are lost in translation. If translation from one or two different languages is required, even claiming idea A is incorrect, it may be any combination of letters since latin is not english, greek is not english, hebrew is not english .. and old english looks more like german than english for example.