Norms and Necessity, by Amie Thomasson

Long review of Amie Thomasson's book Norms and Necessity.
Imagine you’re teaching someone how to play chess. You might start by saying ‘White must move first’, where the word ‘must’ is used to convey a rule. You would have said basically the same thing if you had used the imperative ‘If you’re white, then move first’. And since imperatives prescribe rather than describe, it is natural to think that using a must-statement to convey a rule is importantly different from describing something. More specifically, at least when you are teaching someone a game, the word ‘must’ does not seem to describe what always happens or even to describe what the rule book says but rather to affirm or institute rules.