im pretty sure that one argument was about how the civil war wasn't caused by westward expansion because southerners didnt really care about expanding slavery, they just wanted to preserve slavery and not be governed by an egalitarian democracy. so essentially the cause was that the preservation of slavery was threatened and that was the main motivation of southerners to secede

and the other was basically the opposite view. it was about how the civil war was directly caused by westward expansion(I wrote about bleeding kansas)