The Speaker
The speaker in this poem seems to be a poet, or an avid reader of poetry, who feels strongly about what poetry should mean for humankind. The speaker is likely Archibald MacLeish himself, who is obviously a poet.
"A Poem"
In this poem, the concept of “A poem” is in some ways personified, or at least made into an entity that moves within the realm of the physical. This poetic choice enables MacLeish to explore how a poem should act or unfold for the mind and the senses.