Dante Alighiere, PURGATORIO, Canto XVI

Illustration by Salvador Dali
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As they proceed through the mist, they hear the voices of spirits praying. Marco Lombardo, one of these, points out to Dante the error of such as impute our actions to necessity; explains to him that man is endued with free will; and shows that much of human depravity results from the undue mixture of spiritual and temporal authority in rulers.