Considering Fossil Fuel's Full Cost: Looking at the long term impact of our present use of fossil fuel may help considerably in properly valuing it, and thereby encouraging the healthy development of sustainable energy sources. If one simply notes that our posterity will not have the source to use in emergencies, it would proabably be a big step in that direction. Even our present ability to imagine can bring up significant and persisting concerns, given natures ways, humanity included. That being done, one tends to include the cost of replacing it in some substantive sense so our posterity may address such concerns. On the whole, fossil fuels are probably most validly used as an emergency material.