You ask me: "Did Owen tell you in confidence that he is looking for another position?" He didn't, and in fact Owen and I have never talked about the question. What can I say? It seems I can truthfully and with a clear conscience answer: "No." After all, Owen never confided in me, so I owe him no duties of confidentiality.
But if I make it a policy to answer such questions honestly in cases where Owen has reposed no relevant confidence in me, then I make myself into a non-intentional betrayer of secrets. For you can then tell whether Owen has shared a relevant confidence in me simply by asking me about it—if I answer, then he has not, and if I do not answer, then he has. Moreover, in typical cases you can also deduce, with some probability, what the confidence was. For it is more likely that Owen would take the trouble to request confidentiality about his looking for a new position than about his being satisfied with his present post.
By answering in the negative when no confidence has been reposed in me, then, I decrease my ability to keep confidences on other occasions. It seems, then, that a good thing to say is: "If he did tell me so, I wouldn't be able to share it with you. And if he did not tell me so, I still shouldn't tell you that, since then you'd be able to tell when confidence has been reposed in me."
But what is kind of tricky is that there are cases where this response does not seem satisfactory from Owen's point of view. Suppose that Owen never committed a certain pecadillo, but I am such a close friend of his, that had he done it, he would have immediately told me about it in confidence. If I am asked whether Owen confessed the pecadillo to me, and he had not, then it seems the very best thing for Owen's reputation is a clear denial from me. But a policy of such denials makes me a poorer keeper of confidences for my friends. So there is a bit of a dilemma here.
Presumably, the thing to do is to say that the duty to remain an effective keeper of confidences when one has not had a secret confided to one is only a prima facie duty. It is, simply, a good thing to be an effective keeper of confidences, but sometimes we need to act in ways that makes us less effective at keeping secrets, just as sometimes we need to act in ways that will make us less good racketball players (a philosopher I know gave up a professional racketball career to go into philosophy). To be an effective keeper of secrets is a genuine good, but there are incommensurable goods that might justify becoming a less effective keeper of secrets. There is nothing surprising here. In fact, examples are easy to find. Learning to keep a poker face, for instance, makes one a more effective keeper of secrets, but increases one's temptations to dishonesty.
What is kind of interesting to me about this case is that it seems one has prima facie duties of confidentiality towards people whose confidences one does not actually possess. I think this is because one has good reason to be ready with the offices of a friend (understood broadly—we should be a friend or neighbor to all), and hence to act in ways that make one a more effective friend. Maybe we should see this reason as grounded in what one owes fellow human beings, or maybe in what one owes oneself, or maybe in what one owes God.
And confidentiality is not the only such case. For instance, one likewise has reason to avoid budgeting one's money and time in such a way that one has no margin to help friends in need.
There is nothing earthshaking or deeply surprising here. I just wanted to think through these issues, and as often, my way of thinking them through is by writing.