The arguments that Abraham Lincoln used against the secession of the Southern states include:
B. The government was a union of people, not states. C. The Southern states lacked the power to secede under the Constitution.
While Lincoln did express views against slavery and believed it was a moral and economic issue, the specific argument that "slavery was a system that would eventually bankrupt the Southern states" is not one he emphasized in the context of secession. A and D do not accurately reflect Lincoln's primary arguments against secession.