premise: poetic <mask>; grammatical <mask>, etc.
hypothesis: the best context for <mask> here is That deviation from strict fact, form, or rule, in which an artist or writer indulges, assuming that it will be permitted for the sake of the advantage or effect gained; but not Authority or liberty given to do or forbear any act; especially, a formal permission from the proper authorities to perform certain acts or to carry on a certain business, which without such permission would be illegal; a grant of permission.