Shelley was one of the major English romantic poets. He was a naturalistic atheist per his pamphlet "The Necessity of Atheism" and an advocate of non-violent resistance.
Shelly was an ethical vegan (then called vegetarian). His compassion for sentient beings led him to write: "If the use of animal food be, in consequence, subversive to the peace of human society, how unwarrantable is the injustice and the barbarity which is exercised toward these miserable victims. They are called into existence by human artifice that they may drag out a short and miserable existence of slavery and disease, that their bodies may be mutilated, their social feelings outraged. It were much better that a sentient being should never have existed, than that it should have existed only to endure unmitigated misery"; "Never again may blood of bird or beast/ Stain with its venomous stream a human feast,/ To the pure skies in accusation steaming"; and "It is only by softening and disguising dead flesh by culinary preparation that it is rendered susceptible of mastication or digestion, and that the sight of its bloody juices and raw horror does not excite intolerable loathing and disgust."
Shelley on Wikipedia