casts upon the present; the words which express what they understand not; the trumpets which sing to battle, and feel not what they inspire; the influence which is moved not, but moves. Poets are the unacknowledged legislators of the world.

First, hierophants are priests, usually associated with ancient Greece, who interpret mysteries. Unapprehended means not understood. Finally, legislators, a word we might slide over without thinking about, are, on the surface lawmakers, but the important point is that in making laws they bring incarnation or reality to ideas. A new law—such as civil rights legislation—can change reality.

Shelley is therefore saying, first, that poets are priests like those in ancient Greece who interpret what is mysterious or obscure. Second, they are like mirror, reflecting the future—they have a special insight into what the future might look like. They don't, however, always understand what they are saying when they say it: this means they are conduits or transmitters for ideas. If Shelley were born later in time, he might say poets are like radio transmitters. They move ideas to reality from abstraction by stating them in ways masses of people can understand. Therefore, though they are unacknowledged—get no credit for what they do—poets create or incarnate change through the words they write.

Shelley is saying that language has power and that the words of poets have the power to effect change beyond what the poet can predict or understand. Because, like lawmakers in a parliament or a congress, poets cause change, they too are legislators. However, they can make laws—produce change—for the entire world, not one nation.

At the very conclusion of his essay “A Defence of Poetry,” Percy Bysshe Shelley says of poets,

They measure the circumference and sound the depths of human nature with a comprehensive and all penetrating spirit, and they are themselves perhaps the most sincerely astonished at its manifestations; for it is less their spirit than the spirit of the age. Poets are the hierophants of an unapprehended inspiration; the mirrors of the gigantic shadows which futurity casts upon the present; the words which express what they understand not; the trumpets which sing to battle, and feel not what they inspire; the influence which is moved not, but moves. Poets are the unacknowledged legislators of the world.

In this passage, Shelley makes a number of points, including the following:

• Great poets have enormous insight into the ways in which people typically think and feel and into the motives and ideals of most human beings.  Moreover, they are able to express their insights in powerful language.
• Great poets themselves possess great souls, minds, and spirits, and they use one of the best instruments of communication ever invented (poetry) to express their “penetrating” insights. They know, in the deepest ways possible, what makes most people “tick.”
• Great poets are themselves often surprised by their own insights. Rather than deliberately setting out to produce such insights, they produce them simply by being subconsciously in tune with “the spirit of the age” – that is, with the most important ideas and feelings typical of their historical eras.
• Because they are in tune with the deepest intellectual and emotional impulses of their times, great poets are also in tune with the future.  They can sense, from their familiarity with their own times, what is likely to happen and to be thought and felt in coming years. Often they are not conscious of their insights into the future, but in any case they express those insights in powerful language.
• Often the great poets are not even conscious of the ways they are inspiring the people who read their works.
• For all these reasons and in all these ways, poets are “the unacknowledged legislators of the world.”  In other words, they help shape both the present and the future.  They help affect the ways in which other people both think and act. They write in ways that help inspire the best in those who read them, who then act according to the impulses the poets have helped inspire.  Poets are “unacknowledged” legislators in the sense that few people realize the enormous power they wield. They are also unacknowledged in the sense that the world often pays very little attention to them when they are alive; only after their deaths are most great poets truly appreciated.  Finally, they are additionally unacknowledged in the sense that even they (perhaps especially they) have little sense of the enormous power they are capable of wielding.

We normally think that politicians are the most powerful people of their times, but, according to Shelley, their power ultimately pales into insignificance compared with the great poets of an historical era.