Sentence:  The word `` church '' which turned up over and over again among Jubal 's words gave him knotty difficulty ; there was no Martian concept to match it - unless one took `` church '' and `` worship '' and `` God '' and `` congregation '' and many other words and equated them to the totality of the only world he had known during growing waiting & & & then forced the <WSD>concept</WSD> back into English in that phrase which had been rejected ( by each differently ) by Jubal , by Mahmoud , by Digby . 
Meaning of the word marked with <WSD> tags:  an abstract or general idea inferred or derived from specific instances