Question

Read the following excerpt from the poem “On Imagination” by Phillis Wheatley.

Imagination! who can sing thy force?
Or who describe the swiftness of thy course?
Soaring through air to find the bright abode,
Th' empyreal palace of the thund'ring God,
We on thy pinions can surpass the wind,
And leave the rolling universe behind:
From star to star the mental optics rove,
Measure the skies, and range the realms above.
There in one view we grasp the mighty whole,
Or with new worlds amaze th' unbounded soul.

What does the speaker compare imagination to in the poem?