Forgive me if this is a silly question, but I'm currently reading Simon Winchester's The Professor and the Madman. The book isn't at all about the US Civil War, however it's mentioned that W.C. Minor joined the army and got me thinking on a tangent.
Considering Lincoln's peaceful nature (or at least that's how he is portrayed in popular history), I have a hard time believing he was accepting of a civil war. He'd have known how violent that could have been for the nation and, I would think, take measures to avoid such a war unless it were the last possible solution. Did he see the war as a necessary evil or did he support either side's cause? And does a U.S. president have any power to say "Hey guys, let's not do this"?
Considering Lincoln's peaceful nature (or at least that's how he is portrayed in popular history)
I'm not exactly sure what you mean by "popular history", but you shouldn't make judgements on a real person's character based upon how they are depicted in any sort of fictionalised media like film or TV or novels. Reading up on actual history (especially from contemporaries of Lincoln) will give you a much better understanding of the man as he actually was, not how he was seen by future generations.
I have a hard time believing he was accepting of a civil war.
It wasn't as if he had a choice. The Confederates had already declared themselves to have broken away from the Union. Either Lincoln accepted this (which no president would ever do in their right mind) or he went to war with them.
He'd have known how violent that could have been for the nation and, I would think, take measures to avoid such a war unless it were the last possible solution.
He obviously knew how violent and destructive a war would be. Do you think Lincoln wanted a war? It was the Confederates that started a war when they attempted to rebel against the government. Lincoln simply responded to this act of treason.
Did he see the war as a necessary evil or did he support either side's cause?
Why would the war be a necessary evil? War was the absolute last thing he (and everybody else) wanted, but it happened because the Confederates did not want to be a part of the Union and wanted their own country, and obviously the president of the United States was not going to allow half of his country to split away from the other half. And since Lincoln was the one to defeat the Confederates in the war, I'd say he was pretty firmly on the side of the Unionists.
And does a U.S. president have any power to say "Hey guys, let's not do this"?
Yes, it's called sending in the military, which is exactly what he did.
Are you familiar at all with the war? It seems by your question you might be new to politics, history or war. In which case you might be really asking how the Civil War started. Or perhaps what legal authority Lincoln had to wage war? The US President was and is commander in chief of the armed forces, with Constitutuonal authority to suppress rebellions and insurrections, which is what he considered the Confederacy.