Abraham Lincoln’s Cooper Union Address: A Masterclass in the Geometry of Persuasion

How Euclid’s Method Turned a Speech into a Presidency

Abraham Lincoln delivering his address
at Cooper Union in New York City in February 1860.

In a biography about Abraham Lincoln, one of his contemporaries on the Eighth Judicial Circuit in Illinois, Henry Clay Whitney made this startling comment:

"...it is fair to suppose that in his evolution from a cornfield logician and log cabin orator...his study of the six books of Euclid held a place." [1]

This revelation—that Lincoln studied geometry not for practical application but for intellectual discipline—might seem eccentric. But it echoes a much older tradition. Quintilian, the Roman educator and rhetorician born in 35 AD, argued that geometry was essential to the making of a great orator. In his Institutio Oratoria, he wrote:

"No man, assuredly, can become a perfect orator without a knowledge of geometry. It is not without reason that the greatest men have bestowed extreme attention on this science." [2]

Lincoln and the Geometry of Justice

Lincoln, it seems, was one of those men. His Cooper Union Address [*], delivered in 1860, is widely regarded as a masterclass in rational argumentation. In its first section, he meticulously cited the Founding Fathers—by name, vote, and legislative record—to prove that they opposed the expansion of slavery into the territories. It reads, as many scholars have noted, like a lawyer’s brief: stripped of rhetorical flourish and focused on historical evidence and constitutional logic.

Yet Lincoln’s clarity wasn’t merely legal—it was mathematical. In an age of fiery rhetoric and political spectacle, he stood apart as a disciplined thinker. His study of Euclid’s Elements honed his logical rigor, and at Cooper Union, he applied that geometric precision to the moral crisis of slavery. This fusion of classical logic and political persuasion helped transform him from prairie lawyer to presidential contender—and it remains a masterclass in how reason can illuminate justice.

 Euclid’s Six-Part Structure

From the first six books of Euclid’s Elements about Plane Geometry, Lincoln learned that a proper logical argument has six components:

1. Enunciation – State the proposition.

2. Exposition – Clarify the terms.

3. Specification – Identify what’s being examined.

4. Construction – Lay out the framework.

5. Proof – Demonstrate the truth.

6. Conclusion – Tie it all together.

Lincoln applied this structure like a master geometer—but to political reasoning instead of triangles.

🗣️ Cooper Union Address (1860)

This speech was Lincoln’s intellectual coming-out party in New York City. He argued that the Founding Fathers opposed the expansion of slavery—and he did it with Euclidean precision.

Let’s map the speech to Euclid’s structure:

Euclidean Element	Lincoln’s Speech Example
Enunciation	“The question is: Did the Founding Fathers believe Congress could regulate slavery in the territories?”
Exposition	He defines key terms like “territories,” “regulate,” and “slavery.”
Specification	He identifies 39 Founding Fathers and examines their votes and writings.
Construction	He builds a framework using historical records, laws, and resolutions.
Proof	He shows that a majority of these men supported federal regulation of slavery.
Conclusion	“Let us have faith that right makes might, and in that faith, let us...dare to do our duty.”

Lincoln’s logic was so airtight that even skeptical Eastern elites were won over. It wasn’t just persuasive—it was mathematically elegant.

That said however, Lincoln wasn’t devoid of emotional appeal. The second and third parts of the speech shift tone:

In Part Two, he spokes directly to the South, challenging their claim to be the true conservatives. He reframed "conservatism" as fidelity to the Founders’ ideals, subtly invoking moral clarity.

In Part Three, he appealed to Republicans not to abandon their principles for political expediency. Although its the conclusion to his carefully crafted logic, Lincoln's closing line—“Let us have faith that right makes might…”—is deeply stirring. [3]

So, Lincoln began with reason and ended with moral conviction. It’s not emotion in the theatrical sense, but a kind of ethical urgency that elevates the speech from mere argument to a call for conscience.

Conclusion:

Just as Euclid built geometry from axioms, Lincoln built his moral arguments from historical truths and logical clarity. In the Cooper Union Address, he didn’t rely on fiery appeals or partisan fervor—he reasoned like a philosopher and proved like a mathematician. His words were not just persuasive; they were structurally sound, grounded in intellectual architecture that still resonates today. By fusing classical logic with political conviction, Lincoln transformed a speech into a blueprint for justice—and a moment into a movement.

This is another anecdote about Abe Lincoln, Storyteller.

Mac

[*] There were 1,500 people in the audience on that snowy February night in New York City. One attendee wrote, “No man ever before made such an impression on his first appeal to a New York audience.” [4]

Lincoln’s Cooper Union Address ran nearly 7,000 words. [For comparison, the Gettysburg Address was just 272.] Yet every word was printed in full by The New York Times and circulated widely as campaign literature. Why? Because Lincoln wasn’t just giving a lecture—he was answering Southern Democrats who threatened secession if a Republican won the presidency.

This wasn’t a stump speech—it was a constitutional argument, a moral reckoning, and a political audition rolled into one. And because of Euclid, it worked. Three months later, Lincoln secured the Republican nomination. Six months after that, he was elected president.

📚 Works Cited

[1] Whitney, Henry C. (1908) Life of Lincoln. New York, NY: The Baker & Taylor Company.

[2] Quintilian. Institutes of Oratory. Edited by Lee Honeycutt, translated by John Selby Watson, Iowa State University, 2006. Accessed 4 Sept. 2025

[3] "Collected Works of Abraham Lincoln. Volume 3 [August 21, 1858 to March 4, 1860]." In the digital collection Collected Works of Abraham Lincoln. https://quod.lib.umich.edu/l/lincoln/lincoln3?view=toc. University of Michigan Library Digital Collections. Accessed September 1, 2025.

[4] “And That’s the Way It Was: February 27, 1860.” Columbia Journalism Review, www.cjr.org/the_kicker/and_thats_the_way_it_was_febru_12.php.. Accessed 9 Sept. 2025.