 The Essentiality assumption goes beyond Individuation: Individuation allows that assertion is only actually individuated by N, and that it could have been governed by some other norm. By contrast,  (A4)  holds that assertions could not exist and be governed by a different norm: if assertion were subject to a different norm, it would be a different speech act. Nothing but an assertion could violate the norm, if the  (A3)  and  (A4)  properties hold.