Sentence:  Whereas Bultmann 's `` center '' position is structurally inconsistent and <WSD>is</WSD> therefore indefensible on formal grounds alone , the general position of the `` right '' , as represented , say , by Karl Barth , involves the rejection or at least qualification of the demand for demythologization and so is invalidated on the material grounds we have just considered . 
Meaning of the word marked with <WSD> tags:  have the quality of being; (copula, used with an adjective or a predicate noun)