How is it that you know so much more about the Confederacy than its Vice President?

The new constitution has put at rest, forever, all the agitating questions relating to our peculiar institution African slavery as it exists amongst us the proper status of the negro in our form of civilization. This was the immediate cause of the late rupture and present revolution.

• Alexander Stephens, Vice President of the Confederacy

I mean he literally says slavery was the "immediate cause" of secession. Nothing in there about federal powers.