Duty

So my opinion, which I know will cause you suffering, and for that very reason will persuade you that I do not give it without a great deal of reflection, is that you should leave Mademoiselle de Volanges in the convent, since that is her choice, and that you should encourage rather than oppose the plans she seems to have made. And while you wait for the outcome you should not hesitate to cancel the marriage you have arranged.

(Letter CLXXII, Madame de Rosemonde to Madame de Volanges)