At many large airports these days, one cannot process down the gangway to one’s plane without confronting a series of advertisements for HSBC bank. It’s a catchy, if semantically troubling, campaign. Each ad consists of two pairs of identical pictures boldly labeled with opposite one-word descriptors. For example, an image of a serious-looking young businessman in suit and tie bears the label “Leader” while next to it is an image of legs in ratty jeans and scuffed boots bearing the legend “Follower.” The same images are then repeated with the words reversed: the leader becomes the follower and vice versa. Other image-pairs come labelled “Good/Bad,” “Trendy/Traditional,” “Pain/Pleasure,” “Perfect/Imperfect,” etc. And in case you are slow on the uptake, the Aesop behind the ad includes a helpful moral: “If everyone thought the same, nothing wo ...