Doubt and Trust
In Valeria, Ferdinand heard it was common to get married for common interests like consolidating resources or strengthening the family's power.
However, there were also a lot of instances when people marry for love, or it is mixed with common interests.
Ferdinand had overheard some of his knights and soldiers who married for love, that at times, their wives complained or fought with them, because they misunderstood that aside from common interests, all they ever actually wanted was getting laid. Not making love, but only the act to sate one's lust.
Ferdinand didn't want Arabella to think that all he ever wanted was her body.
Sure, he desired her and lusted for her like crazy. But his desire did not stem only from physical need. He wanted Arabella as a whole, not only her body.
It was why Ferdinand tried to express it in words so Arabella would not misunderstand his desire like the wives of the knights did.
