Civilization as we know it depends on cheap oil. It won't come to an end, but nothing will work on the same scale as now for some time to come. I'm not suggesting giving up on alternatives, but they won't let us avoid a major reduction of scale in our way of life. The production of things like oil shale and tar sands cannot equal light sweet crude. At some point, it takes more energy to extract and refine than you get in return. Combine that with ever increasing demand, and it points to collapse. Is it really so bad to imagine an agricultural instead of an industrial based economy?