Sentence:  Incurably optimistic , dogmatic , and utterly fearless , in his youth a devout Baptist , in spite of his friendship for the Quaker poet John Greenleaf Whittier ( 1807 - 1892 ) he eventually attacked the orthodox churches for what he deemed their cowardly compromising on the slavery issue and in his invariably ardent manner <WSD>was</WSD> emphatically unorthodox and denied the plenary inspiration of the Bible . 
Meaning of the word marked with <WSD> tags:  have the quality of being; (copula, used with an adjective or a predicate noun)