Not only did Chaucer provide English poetry with fresh subject-matter, treated, as we have seen, with rich fancy, learned allusion, and uncommon humour; but he displayed the deftest metrical skill of any English poet before Spenser. His ability in the art of versification appears even more remarkable when we remember that, in the absence of one definite and established English poetic usage, he had to decide his own problems of diction and metre. No English dialect, before Chaucer wrote, was quite definitely the language of polite and courtly verse. Chaucer made the polite English of court, with its strong French element, so inevitable, that the other English dialects for the first time began to sound rustic and ignorant. When Chaucer began to write, the adequacy of recurring rhythm and rime was not entirely unquestioned. It was being challenged by a revival of alliterative verse in the Old English style by poets of the West of England. Chaucer's success established the two chief principles of English verse —namely, that its rhythm is determined by stress, and that its normal rhythm is rising or " iambic."