This thesis aims to understand Percy Bysshe Shelley's attitude towards the role of the poet in society as an usher of progressive change. To do this, it examines his metaphysics, chiefly his contact with the doctrines of idealism, which crystallised at the dawn of his life through his intimate relationship with the works of Plato, the early engagement with French materialists, English philosophers like Priestley and Hume & a later one with Lucretian materialism, and his deep entanglement with the first modern proponent of anarchism, William Godwin - who could be described as a perfectionist by some or as utilitarianist by others. By doing that the thesis seeks to shed light on how these doctrines influenced Shelley and how he conversed with and critiqued them, revealing the intricacies of his work because, in Shelley's philosophy, the nature of differentiation between the two, that is between materialism and idealism, is notoriously problematic. The beginning of the thesis serves to engage with Shelley's early contact with materialist doctrines, their fast repudiation in their pure form and his later critique in "Cloud" and response to them. The materialist influences of Shelley are pondered, as well as some of the possibilities of interpreting Shelley in a materialist way. Next, Shelley's...