"Had I known then" is followed by some kind of a wish of fortune telling. "Had I known the winning lottery number!" "Had I known my hometown's property value would quadruple!" "Had I known my spouse was going to cheat on me!" I'm going to be honest: I spent a lot of time in my life thinking these thoughts too.The most common story I tell to young adults is, I didn't know there was a field of study called linguistics.Had I known linguistics was a thing in high school, I think I would have had...