Erasmus (ALERT: SPOILERS)
ALERT: SPOILERS
The name of the foreign exchange program in the film is Erasmus. Despite the bit in the film where Xavier looks up Erasmus in the Internet, the real meaning of the name is withheld in the film.
Erasmus' most well-know work was his 1511 essay "The Praise of Folly" (public domain English translation available from Project Gutenberg http://www.gutenberg.org/etext/9371).
The work is "An oration, of feigned matter, spoken by Folly in her own person." It discusses the superiority of folly (or foolishness) over conventional wisdom.
This is what The Spanish Apartment is really about.
At the end of the film, Xavier goes back to Paris where he gets the job his graduate work in Spanish economics prepared him for. Wisdom would tell a twenty-five year old man that a taking a respectable job is a smart thing to do as it will bring him money, respect, prospects for advancement....
Xavier doesn't listen to Wisdom--he listens to Folly and runs away to become a writer.
The same theme is played out again and again in the film.
When Wendy wants to stay in her room and write in her diary instead of going out with all of her roommates to clubs and bars, she is listening to Wisdom. When she, at Xavier's bidding, joins her friends for a drunken night on the town, she is listening to Folly.
Xavier's involvement with married Anne-Sophie is hardly a wise decision. Rather, it's pure folly. And that's what the film celebrates.
That's why Xavier keeps seeing visions of Erasmus.
After Xavier's brain MRI, he is pronounced normal by the cuckolded doctor Jean-Michel. That's the film's main point--to argue that that Folly is a normal condition and preferable to societal and parental Wisdom.
--Johnson 1740