Read the following passage and answer the question. 'Brother Boniface preached fire and brimstone on Sundays, yet on Mondays his hands were deep in the church treasury. He thundered against corruption from the pulpit with the same mouth he used to negotiate bribes in the vestry. The congregation, blinded by his eloquence, saw only the shepherd and never the wolf.' The expression 'saw only the shepherd and never the wolf' is a reference to the literary device known as