Every so often, one should stop ascribing blame and prescribing remedies and put down exactly what one thinks is likely to happen. As George Orwell observed, this can be a humbling experience, because our predictions so often reflect our hopes or fears rather than careful analysis. Besides, castigating politicians one dislikes, and concocting policies that have no chance of encountering the test of practice, is much more fun than peering into the future. Yet no other topic could benefit more from a cold-blooded analysis of the probabilities than the current conflict in Syria and Iraq and the various burning...