There are several causes but if you don't include among them, the desire on the part of the Southern states to protect the institution of slavery and to perpetuate its spread into the territories, you're not being honest.
There is a quite vocal contingent on FR which will basically baldly assert that slavery had NOTHING to do with the Civil War........routinely crack me up. As if the war would have been fought entirely over tariffs or something. It's a ridiculous overreaction to the somewhat inaccurate portrayal of the Civil war as ONLY being about slavery.
Maybe, but you're not being honest if you're trying to claim that the North's opposition to slavery (such as it was) was based on concern for the slaves.