Sentence:  The tragic irony of the play is that the very belief in and concern with a devil who could be met in the woods and combatted with formulae set out in books was the very thing that prevented them from detecting the <WSD>real</WSD> devil when he came among them . 
Meaning of the word marked with <WSD> tags:  being or occurring in fact or actuality; having verified existence; not illusory; not ghosts"