subdues to union

As described in Percy Bysshe Shelley?s A Defence of Poetry, poetry ?marries exultation and horror, grief and pleasure, eternity and change." This description of the marriage of two extremes is reminiscent of William Blake?s The Marriage of Heaven and Hell. Blake wrote about expanding one?s thoughts and not settling on one interpretation. However, Shelley?s description differs from Blake?s in that union within ?The Marriage of Heaven and Hell? seems to push the physical limits of man. To marry any two extremes was to push beyond normal boundaries of thought and engage fully with the imagination. Shelley?s description of a similar union through poetry does not seem to help man break through mental boundaries. Rather, that unity seems to control and pacify ideas which seem to clash. Shelley writes that poetry ?subdues to union under its light yoke all irreconcilable things.? Where Blake would have glorified the clash created by the union of ?irreconcilable things,? for example, a marriage of Heaven and Hell, Shelley unites two extremes through poetry, but this unity, he claims, ?subdues? that which is irreconcilable.