"They Must Upward Still, And Onward, Who Would Keep Abreast Of Truth"

Context: In the 1840's the question of slavery was already a burning issue in the United States; many, in both North and South, had come to the conclusion that slavery of other human beings was wrong, regardless of the question of race. As the war with Mexico seemed a probability, men of perspective in the North, especially in New England, foresaw that it could be interpreted as an opportunity to bring additional slaveowning territory into the Union. Such far-sighted men spoke out, as Lowell does in this poem. Lowell proclaims that mankind must continue to seek good, must not be impressed or imprisoned by the past; he calls the people of the "Mayflower" iconoclasts, and bids their descendants be not cowardly in looking at the evils of slavery; he challenges New Englanders to break with slavery as their forefathers had broken with ecclesiastical institutions. He calls slavery one of the "Sons of Force and Darkness, who have drenched the earth with blood," and he asks, "Shall we guide his gory fingers where our helpless children play?" He ends the poem with the following stanzas:

They have rights who dare maintain them; we are traitors to our sires,
Smothering in their holy ashes Freedom's new-lit altar-fires;
Shall we make their creed our jailer? Shall we, in our haste to slay,
From the tombs of the old prophets steal the funeral lamps away
To light up the martyr-fagots round the prophets of today?
New occasions teach new duties; Time makes ancient good uncouth;
They must upward still and onward, who would keep abreast of Truth;
Lo, before us gleam her camp-fires! we ourselves must Pilgrims be,
Launch our Mayflower, and steer boldly through the desperate winter sea,
Nor attempt the Future's portal with the Past's blood-rusted key.