In nearly four decades of life as an American, I’ve heard a whole lot of conflicting things about the Civil War. Probably the most contentious point is about what slavery had to do with it. My own elementary education made clear that the principal issue in the war was slavery, but that this issue was mixed up with more general disputes about states’ rights and federal authority. That same education made it clear that the North fought the war primarily in order to end slavery, but also to “preserve the Union.” It was only in early adulthood that I learned that this is apparently not how the Civil War is presented to many young Americans and that there is a lot of disagreement about it. Evidently many, maybe most, kids are taught that the war was primarily about states’ rights and that slavery was a secondary issue. People — including historians who actually have some claim to know what they’re talking about — disagree about exactly what combination of factors motivated the North to fight. But a fair number of people I’ve encountered, mainly people without any historical credentials but a few with some, have barked at me about how the Civil War wasn’t really about slavery at all, but was entirely about economics; slaves mattered for that reason, but for that reason only.
I’m not about to enter into this dispute. I do, however, find it worth noting what J.S. Mill — yep, him again — thought about the war and his report of English opinion about it. No doubt historical causation is complicated, but it is interesting that, to an outside observer at least, this war was very definitely about slavery, and immensely important.