It occurs to me that Marianne was logically at the back of the queue where Willoughby "engaging his faith" was concerned. By the time he met Marianne his "honour" was already bound to at least one woman, almost certainly two, and quite possibly others besides.

He was bound in honour to Eliza by his seduction of her and by getting her with child - a matter of honour serious enough to fight a duel over.

He says he "had reason to be secure of" Sophia if he chose to propose marriage to her. To be this secure of a £50,000 heiress, who must have had some other suitors even though she wasn't a great beauty, suggests to me that he must have "endeavoured to make himself pleasing to her" and engaged her affections at least as much as he did with Marianne.

Willoughby also says that with Marianne he was "giving way to feelings which I had always been too much in the habit of indulging". So how many other girls had he treated in a similar Manner? It sounds as though the queue could have been quite a long one!