If they’re French, even dweebs get to lounge around tastefully beige Paris interiors, clutching long-stemmed glasses of Merlot while discussing the potential collateral damage of an exploratory kiss on the lips. In Emmanuel Mouret’s comedie d’amour, the writer-director plays a skinny, cow-eyed math teacher who asks his best friend, a skinny, sloe-eyed, and very married scientist, played by Virginie Ledoyen, to kick-start his dormant libido. She agrees with misgivings, the two rationalists fall helplessly in love, and from that moment on, in this more masturbatory than carnal folie, they never shut up. The interesting question buried in all this gassing on about whether we want what’s forbidden because it’s forbidden and whether it’s all worth the bother and who will get hurt, hinges on the battle between desire and—is it ethics or etiquette? I couldn’t quite tell. To Mouret’s credit, he doesn’t dismiss the question as trivial or bourgeois. But despite the tale-within-a-tale structure that spells out what’s at stake, the director is so much more reluctant than his fastidious characters to play the moralist, which means that Shall We Kiss? (a title that implies a different line of inquiry from the more assertive French, Un Baiser s’il vous plait) bogs down in the philosophical shallow end and never quite recovers from what’s clearly meant to be a deceptively light tone.