Sentence:  If the photographically realistic continuity of dreams , however bizarre their combinations , denies that it <WSD>is</WSD> purely a composition of the brain , it must be compounded from views of diverse realities , although some of them may never be encountered in what we are pleased to call the real life . 
Meaning of the word marked with <WSD> tags:  have the quality of being; (copula, used with an adjective or a predicate noun)