Sentence:  I was having lunch not long ago ( apologies to N. V. Peale ) with three distinguished <WSD>historians</WSD> ( one specializing in the European Middle Ages , one in American history , and one in the Far East ) , and I asked them if they could name instances where the general mores had been radically changed with `` deliberate speed , majestic instancy '' ( Francis Thompson 's words for the Hound of Heaven 's pursuit ) by judicial fiat . 
Meaning of the word marked with <WSD> tags:  a person who is an authority on history and who studies it and writes about it