That Bouguereau was having trouble might say something about problems in viewing portraiture this way, because it severely limits it to things you can relate.

I'm the one who uploaded that picture into the files section, in order to show that his paintings looked completely different from his sitters, or even from photographs for that matter, as a way of showing Bouguereau and similar artists weren't interested in photographic representations. Its a misunderstanding that their paintings are like photographs. Thomas Couture wrote in his book with disdain towards Realists, stating that artists who called themselves Realists did not see truth in nature, but mistook ugliness for truth, while it was rather a lack of understanding what they saw. He believed this masked their lack of talent. To see truth in nature to him was to be able to represent the truth of what you saw, which in art meant having a visual understanding of things in nature, and representing it, instead of simply copying patterns disjointedly.

Couture himself was an accomplished portraitist. Somewhere he talks about art as finding beauty in nature, and not simply portraying it, but exalting in its beauty so as to reveal it to others.

'Realism' was a shift in attitude from academic painters, which saw that way of painting as false and constructed.