Since at least the Middle Ages, philosophers and philologists have dreamed of curing natural languages of their flaws by constructing entirely new idioms according to orderly, logical principles. Inventing new forms of speech is an almost cosmic urge that stems from what the linguist Marina Yaguello, the author of “Lunatic Lovers of Language,” calls “an ambivalent love-hate relationship.” Language creation is pursued by people who are so in love with what language can do that they hate what it doesn’t.