Italian Renaissance authors produced works including Niccolò Machiavelli's ''The Prince'', an essay on political science and modern philosophy in which the "effectual truth" is taken to be more important than any abstract ideal; Ludovico Ariosto's ''Orlando Furioso'', continuation of Matteo Maria Boiardo's unfinished romance ''Orlando Innamorato''; and Baldassare Castiglione's dialogue ''The Book of the Courtier'' which describes the ideal of the perfect court gentleman and of spiritual beauty. The lyric poet Torquato Tasso in ''Jerusalem Delivered'' wrote a Christian epic in ''ottava rima'', with attention to the Aristotelian canons of unity.