I play in a 5e game, and a monk was getting shot in the back of the head. One of the monk's abilities is Deflect Missiles: "Starting at 3rd level you can use your reaction to deflect or catch the missile when you are hit by a ranged weapon attack." (PHB53 p.78, emphasis mine.)
We argued that it doesn't say “see” in the book, but wouldn't he have to see it to know the attack is coming?
Can a monk deflect an incoming missile even if he can't see it?