In an earlier question (http://www.amherst.edu/askphilosophers/question/875) the following was asked: "Am I morally bound to tell my sex partner if I fantasize about someone else whilst making love to her? Or the subject of the fantasy for that matter?"
T. Pogge responded: "Now ask yourself whether such disclosures from her would really be in your interest: Would you want to know what she fantasizes about when the two of you make love? Would you be happier if she gave you this information, or do you think she would be happier if she gave it to you?"
Is the duty to disclose determined by self-interest? (how many people are sufficiently aware of their self-interest to thus determine their duties? e.g. how many people enact patterns of self-destructive behavior, particularly in their sex and/or love-lives?) Can the duty to disclose be determined by the interest of the person to whom the duty is owed? (How many people know what is in the interest of another person? particularly, again, with regard to their emotional ties, sex lives and/or love-lives?) Final question: are our interests (never mind our duties) determined by their likelihood to promote our or others happiness? Perhaps the fantasy indicates actual preferences rather than mere associative pleasure. Perhaps it doesn't. What is the liklihood that we can tell the difference between the two? Deeply hidden desires can masquerade as fantasy.