The nature of Antonia's attack is that she advocates a passionate committment
in life. To Decoud she represents, literally, the attractiveness of the dream-ideal.
Again his skepticism is belittled by the narrator, demoted to a mere "pose"
and "affection." But the rest of the paragraph, showing Antonia's hold
over his mind for years, suggests an ongoing struggle between rather deeply-held
points of view.