I am always intrigued by Colonel Brandon's conversation with Elinor in Ch. 11. He's trying to find out what Marianne thinks about second attachments, asks Elinor some very particular questions about Marianne's views, and reveals something of his own romantic past.

The whole conversation is full of things to discuss, but this part, in particular, intrigues me:

"Does your sister make no distinction in her objections against a second attachment? or is it equally criminal in everybody? Are those who have been disappointed in their first choice, whether from the inconstancy of its object, or the perverseness of circumstances, to be equally indifferent during the rest of their lives?"

"Upon my word, I am not acquainted with the [minutiæ] of her principles. I only know that I never yet heard her admit any instance of a second attachment's being pardonable."

"This," said he, "cannot hold; but a change, a total change of sentiments -- No, no, do not desire it, -- for when the romantic refinements of a young mind are obliged to give way, how frequently are they succeeded by such opinions as are but too common, and too dangerous!

When he says 'This cannot hold', what is really meant by 'this'? Since it follows right after Elinor's comment that Marianne won't admit to a second attachment being pardonable, does he meant that it is impossible to hold onto such an opinion about second attachments?

The second part of that speech--about the romantic refinements of a young mind, etc. is almost a repeat of what he just said to Elinor a moment earlier : "something so amiable in the prejudices of a young mind, that one is sorry to see them give way to the reception of more general opinions."