Sir Philip Sidney

 Sir Philip Sidney (1554-1586) may not have had a modern theory of language but wrote in his famous Apology, "only the poet, disdaining to be tied to any such subjection, lifted up with the vigor of his own invention, doth grow in effect another nature," which sounds pretty modern to me.

The idea too that a sincere apology (not at all what Sir Philip was driving at necessarily) is the best defense rings true to a poet who once started a poem with the words, "I'm sorry, I'm sorry, I'm sorry."

Sidney's essay can be found in "Critical Theory Since Plato," (Harcout Brace. 1971) edited by Hazard Adams, then a professor at UC Irvine, a compendium of writings of lit crit from Plato to a man named Murray Kreiger.