What caused the American Civil War?

Greetings, Flutherites, I have a question for you, but first, some backstory:

For my Civil War Historiography class, I will be randomly assigned a position to argue in a debate: either that the American Civil War was caused by state’s rights violations, or by slavery.

I am well aware that both of these explanations are ridiculously oversimplified and this argument has been reduced to a contrived either-or scenario (the professor has admitted this as well).

I will be assigned to argue one of these two positions at random by having my name drawn out of a hat. I think that I can effectively argue either side on my own, but being a 3-dimensional thinker, I’m having a hard time reducing the causes of the War to one of these two simplified explanations, and I need some assistance.

That is where you step in, dear reader. Tell me, was the Civil War caused by slavery? Or was it a conflict over state’s rights? If you can provide further reading or citations, I would be much obliged. Thank you.