Is oil like red meat or is it like tobacco? Your answer to that question determines how you feel about the North American boom in unconventional sources of fossil fuel, particularly the Canadian oil sands.

If you think oil is like tobacco, it is a strictly noxious commodity, which seriously harms its users and those around them. We should stop consuming it at once and at all costs. But if you think oil is like red meat, you take a more nuanced view. For the health of the planet, we should find greener alternatives to it whenever we can, but used wisely and in moderation it has an honorable role in the 21st-century economy.

This morality play is being acted out with the greatest intensity in the fight over the proposed Keystone XL pipeline, which would stretch from Canada to the Texas Gulf Coast.

“Keystone is really a symbol of oil, it is very emotive,” Daniel Yergin, the Pulitzer Prize-winning energy expert and chairman of IHS Cambridge Energy Research Associates, told me. “It is probably the most famous pipeline in the history of the world, and it hasn’t even been built yet. It is a symbol around which the opponents of hydrocarbon have rallied.”

Last autumn, the consensus view was that the pipeline would be approved after the U.S. presidential election, no matter who won. In recent weeks, those odds have shifted.