Dear Economist,

I’ve fallen in love with my best friend. Whenever we go out, we have the best of times but for a reason I seem to unable to comprehend, she has not clearly indicated that she feels the same for me as I do for her. I see a risk of alienating her as a friend if I tell her how I feel for her. Quite an exposure in my view.

Any suggestions?

F, Austria

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Dear F,

Economics now devotes much attention to the study of knowledge, and economists distinguish between “mutual knowledge” - you know you love her and she knows you love her, but you do not know that she knows - and “common knowledge”, where you know that she knows that you know that... ad infinitum.

The distinction might seem over-fine, but in your case it may be critical. The most likely scenario, frankly, is that your friend can read you like a book but prefers to ignore your crush. The ambiguity of mere mutual knowledge preserves your friendship, but a declaration of love would create common knowledge and doom it.

The alternative possibility is the one you hope for: she loves you but does not know of your love. You need to discover whether this is true without risking all, so simply ask a friend of hers to make inquiries.

Another option, of course, is to write a letter to the FT. If your friend is pretending not to notice your ardour she can also pretend not to notice your letter. The fatal transparency of common knowledge is avoided and your friendship can continue.

If by some miracle she loves you but is blind to your feelings, your letter will solve this problem. Fingers crossed for the next few days, eh?

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