In my freshman logic course, now a long time ago, I learned about Petitio Principii, Circulus in Probando, also known as arguing in a circle. It's a basic fallacy popularly demonstrated in a formulation like this: Daniel always tells the truth. I know this because he told me so.

But of course Daniel might be lying, right?

I do not know the academic background of American Petroleum Institute's Marty Durbin, but it's very possible, given his recent comments, that he didn't take freshman logic. Or maybe he did and he's learned to apply his lessons in very clever ways. You be the judge.

My suspicion over Mr. Durbin's schooling comes from his comments regarding the expansion of the Keystone XL pipeline, which recently began carrying tar sands oil from Alberta to Oklahoma.

In response to regulatory action taken after two recent spills, Mr. Dubin said that the accidents actually prove the pipeline is safe and should be expanded. Comments on the expansion were due to Secretary of State Hillary Clinton yesterday.

Said Mr. Dubin in The Hill:

What we've seen over the last several weeks here is it's almost proven that we have an effective regulatory process in place... In some ways it actually supports the approval of the XL pipeline. They were able to detect the problems very quickly and take actions to stop the flow through the pipeline.

Of course if no oil were to spill that would also prove that the pipeline was safe. It's nice to be able to have it both ways, but it's not accurate.

Here is what is accurate: If the plan is accepted and the pipeline is expanded, stopping climate chaos will become even more difficult, maybe impossible. Just ask NASA's James Hansen, who wrote this to his scientific colleagues yesterday:

Easily available reserves of conventional oil and gas are enough to take atmospheric CO2 well above 400 ppm. However, if emissions from coal are phased out over the next few decades and if unconventional fossil fuels are left in the ground, it is conceivable to stabilize climate.

Phase out of emissions from coal is itself an enormous challenge. However, if the tar sands are thrown into the mix it is essentially game over. There is no practical way to capture the CO2 emitted while burning oil, which is used principally in vehicles.

Tar sands oil is the worst type of oil for the climate, producing three times the greenhouse gas emissions of conventionally produced oil because of the energy required to extract and process tar sands oil. No amount of rhetorical trickery will erase that fact. Expansion of the tar sands must be stopped.