How is "Ode to the West Wind" a revolutionary poem?
The best place to turn to in this brilliant poem to answer this question would be the final stanza, where Shelley seeks to identify himself so completely with the West Wind that he has spent the whole poem extolling that he is able to spread his ideas and birth new ways of thinking around the world. Pay particular attention to the following quote:
Drive my dead thoughts over the universe
Like withered leaves to quicken a new birth!
And, by the incantation of this verse,
Scatter, as from an unextinguished hearth
Ashes and sparks, my words among mankind!
Be through my lips to unawakened earth
The trumpet of a prophecy!
Note the imagery of these lines. Shelley implores the wind to scatter his "dead thoughts" so that they can be like seeds that will take root and flourish, or he says his words are like "Ashes and sparks" that can be blown around to be kindled back into life and start new fires where they land. These two powerful similes would allow the West Wind to become "The trumpet of a prophecy" as these thoughts and ideas are spread around the world, take root and flourish. Shelley, as other Romantics were, was greatly impressed with the ideas and values behind the French Revolution, and here we can see his desire that his thoughts and ideas might be spread to cause a similar change in thinking and living.