Because I know everyone is wondering what I think of the President's plan for combating the Daesh Cutthroats (formerly known as ISIL or ISIS or Islamic State), I thought I would read up so I can tell you.
Bottom line: Anyone who claims to be certain about what is right is a fool. Both fighting and leaving them alone are moves in an extraordinarily complicated chess game. Either way, there are risks. However, Obama knows more than you and I do so I guess he's more likely to be going the right direction.
Letting them continue unimpeded could allow the consolidation of a huge power bloc that would in every way be dangerous to American interests. Neither Obama (apparently) or I (for sure) believe that there is any meaningful danger to us, here but, allowing these people to become substantial players on the world stage will certainly result in our lives becoming worse.
However, engaging them is expensive and carries risk of the 'Guantanamo penalty', that is, it might motivate the bad guys much more than it's worth. I don't consider it very likely that we will be forced into a large engagement. At least, not as long as Obama is president. (If you allow a Republican to run the military, they will find a way to start a war no matter what. This will only make it sooner.)
To calculate the correct answer means figuring out how it will effect Assad of Syria and his opponents, Iran, Sunnis and Shiites in Iraq, Saudi Arabia, Israel and, don't forget, Russia. (And leaving out the Kurds and numerous other groups who are unlikely to be a huge risk factor.) This is a maniacally complicated situation that is the essence of the mathemtical definition of chaos.
My personal summary of the idea of 'chaos theory' is that every real-world calculation requires several steps and that, at each step, the situation can only be known within a certain margin of error. After an amazingly small number of steps, the multiplication of the errors in each one means that the error function of the result you are trying to determine is so great that your prediction is meaningless.
Dealing with the Daesh Cutthroats will require a long series of actions. Each of them will have unpredictable results. I repeat, anyone that purports to know how it will turn out is a fool.
By that I mean, if you are strongly opposed to Obama's decision for us to become involved in this or if you think he is being too weak, your certainty alone is evidence of intellectual failure. It is fair to like it, or not like it, but thinking that you know the correct answer is foolish. I'm guessing that, if Barack Obama were here to discuss it, he would say the same thing.
He has to make a call. That's his job. I'm no more enthusiastic than anyone about this but, he knows more than I do.