Percy Shelley wrote his most ambitious poem in the summer of 1817 called “the Revolt of Islam”. In this poem, the plot centers on two characters that start a revolution during the time of the Ottoman Empire. “This work demonstrated how Shelley had come to a mature insight into the complex relationship between good and evil”. In this work, he identified and aligned himself strongly with the notion of atheism.
Source: http://www.notablebiographies.com/Sc-St/Shelley-Percy.html
-Gabbi Firrincieli