Final answer:
The quotation reveals that the North and South were deeply divided over slavery, each viewing the other with suspicion, which led to Seward's idea of 'irrepressible conflict' suggesting that differences might only be settled by choosing one societal structure over the other—leading to the Civil War.
Step-by-step explanation:
The quotation outlines the deepening division between the North and South over the issue of slavery; with the North perceiving a conspiracy to dominate politics by slave powers and the South seeing an aggressive abolitionist movement. The concept of an irrepressible conflict as introduced by William H. Seward suggests that tensions had reached a point where the nation would have to choose to be entirely free or slave-holding. The perspectives on liberty and the American Revolution were polar opposite, demonstrating that while the two regions were fighting for what they believed to be their constitutional rights and liberties, their understandings were fundamentally different. This difference in interpretation and adherence to their respective causes was so significant that it hinted towards war as the ultimate resolution to their irreconcilable differences.