Antipope Felix V
Among contemporaries he passed for one of the most formidable polemical or gladiatorial rhetoricians; and a considerable section of his extant works is occupied by a brilliant display of his sarcastic wit and his unlimited inventiveness in "invectives". One of these, published on the strength of Poggio's old friendship with the new pontiff, Nicolas V, the dialogue "Against Hypocrites", was actuated by a vindictive hatred at the follies and vices of ecclesiastics. This was but another instance of his lifelong obstinate denouncing of the corruption of clerical life in the 15th century. Nicholas V then asked Poggio to deliver a philippic against Amadeus VIII, Duke of Savoy, who claimed to be the Antipope Felix V — a ferocious attack with no compunction in pouring on the Duke fantastic accusations, unrestrained abuse and the most extreme anathemas.