There was a genre of writings that were published extensively in nineteenth-century Vietnam called morality books (thiện thư 善書).
Morality books were texts that had originally been revealed in China by spirits such as Wenchang Dijun (Văn Xương Đế Quân) and Guangshang Dijun (Quan Thánh Đế Quân). They encouraged people to live in accordance with Confucian moral standards, but they used the logic of karmic retribution to encourage people to do so.
In other words, they would teach you that if you are filial (hiếu 孝), then good things will happen to you, and if you are not filial, then bad things will happen to you.
Within the genre of morality books, there were different sub-genres. One sub-genre was that of “ledgers of merit and demerit” (công quá cách 功過格). Over 20 years ago, Cynthia Brokaw published an excellent study on the history of this type of text in China, The Ledgers of Merit and Demerit: Social Change and Moral Order in Late Imperial China (Princeton University Press, 1991).
No one, as far as I know, however, has written on the history and existence of these texts in Vietnam, but they did exist. I have come across several ledgers of merit and demerit that were published in Vietnam in the nineteenth and early-twentieth centuries, such as one that was supposedly revealed by Wenchang Dijun and which was included in a text that was compiled and published in 1836 entitled the Summary Materials for Awakening the World (Giác thế tập yếu 覺世輯要).
The way that ledgers of merit and demerit worked is that they contained lists of actions that would either enable someone to gain merit for good deeds (công 功) or lose merit for misdeeds (quá 過). Further, this was all quantifiable.
So, for instance, for each day that you pleased your parents by talking about the morally upright behavior of people in antiquity, you would receive one merit point (每日談論古人善行以悅親一功). If, however, you had poor parents and you did not take care of them, then each day you would accrue ten demerit points (親貧不顧養每日十過).
Then at the end of a ledger of merit and demerit was a kind of chart where you could record the number of merit and demerit points you had accrued each day for a month, and then at the end of the month you were supposed to add this all up to see where you stood.
If your merit points outnumbered your demerit points, then that was good. If, however, it was the other way around, then you would know that you had to do something to improve your situation.
One quick way for a guy to boost his merit points was by getting married. In particular, the ledger of merit and demerit in the Summary Materials for Awakening the World indicates that a guy could gain 10,000 merit points for getting married. But to get those points he had to marry a certain type of person.
Today when guys think about getting married, I think that in general they have the desire to marry someone attractive. According to the ledger of merit and demerit in the Summary Materials for Awakening the World, however, that will not gain a guy merit points. Instead, the opposite was the case.
“If a man marries a woman who is ugly, blind, deaf, mute or ill, and does not despise and abandon her, then he will get 10,000 merit points.” (娶醜貌盲聾疸亞之妻不厭棄萬功)
10,000 merit points!!! Wow!! That could balance out a lot of bad deeds. . .
What is even better is that this same guy could still get angry with his ugly wife, because each time that he got fed up with her and scolded her he would only get one demerit point (娶而厭罵，每次一過).
Meanwhile as for the wife, if she disliked the fact that her husband had an ugly face, then she would gain 1,000 demerit points (嫌夫貌醜千過). . . but, unlike a man who married an ugly woman, the text says nothing about her gaining any merit for marrying an ugly guy in the first place.
In the end, it is always difficult to know to what extent texts like this one show us reality. Nonetheless, they do at least give us a sense of a kind of mindset. At the very least they show us the ideas that might have been used to get people to accept a world in which they did not marry out of their own will, and in which men and women were not considered to be equal.