But the answer is that the devil really is in the details. You could design an intensity-based system that achieved real reductions and did the job. The issue is where you set the intensity knob. So if you set a very long-run, clear target and really ground intensity down, you could do the job with intensity.
So the problem isn't intrinsically intensity; the issue is actually doing something, providing a real, clear carbon price. Whether it's through intensity or total caps is almost a sideshow.