Sentence:  It <WSD>is</WSD> doubtful that Utopia is still widely read because More was medieval or even because he was a martyr - indeed , it is likely that these days many who read Utopia with interest do not even know that its author was a martyr . 
Meaning of the word marked with <WSD> tags:  have the quality of being; (copula, used with an adjective or a predicate noun)