Sentence:  That after all his years of effort to become a composer , he should now , now when he was still stoutly replying to the critics of his Discourse on the Arts and Sciences , <WSD>be</WSD> so close to a success in music and have to reject it . 
Meaning of the word marked with <WSD> tags:  have the quality of being; (copula, used with an adjective or a predicate noun)