That's what it means." "What you do mean, I think, is this;--that you owe a duty to your aunt, the performance of which is not altogether agreeable.
Nevertheless it would be foolish in you to omit it." "It isn't that;--not that at all.

It would not be foolish, not in your sense of the word, but it would be wrong.

My aunt has been kind to me, and therefore I am bound to her for this service.

But she is kind to you also, and yet you are not bound.

That's why I complain.
You sail away under false pretences, and yet you think you do your duty.