He did not say that it was not about slavery. Again, if it was an issue that could be expressed in a single sentence, it would not have inspired the many studies that it has. That is not to deny that the Civil War was about slavery, which I am certainly not. As to what Graham believes, a single sentence means only that. And does not mean he thinks its opposite is true. Not everything is an either/or proposition. Quite often things are more a both/and situation.