Sentence:  This <WSD>is</WSD> not to say that the only explanation of the present infatuation with Norman Vincent Peale 's `` cult of reassurance '' or the other types of a purely cultural Christianity is the ever-present need for a demythologized gospel . 
Meaning of the word marked with <WSD> tags:  have the quality of being; (copula, used with an adjective or a predicate noun)