Stendhal, who once called the beautiful une promesse de bonheur (Nietzsche p. 104). (Linked to audio of the phrase!!)
I think this quote is very interesting. Stendhal who is the one who said “the beautiful une promesse de bonheur” which translates to “beauty is but the promise of happiness”. Stendhal is saying that it is possible to love the ugly if they promise you happiness in the future. He is teaching readers that beauty has little to do with physical perfection and lies far from the physical characteristics of the object at hand.
Stendhal uses this quote in French rather than translating it to English (consistent with the rest of the text) because he wants to keep the saying as close to discovering the actual meaning of the words. The speaker, knowing multiple languages, can become detached when simplifying the words enough to translate into another language. Keeping the phrase in French helps make the saying as pure to the original intent as possible.