The politics of climate change are excruciatingly difficult. Do we make heroic efforts (involving more regulations, subsidies or energy taxes) to curb emissions when any U.S. decreases would have only a tiny global effect? Barring major technological breakthroughs, influencing climate change seems difficult, if not impossible. There aren’t yet sufficient practical alternatives to a heavy reliance on fossil fuels.

Why are Americans so disillusioned with politics? One reason is that our leaders — and this applies to both parties — often create narratives that seem uplifting and convincing only because they are completely detached from underlying realities. These fantasies transcend routine rhetorical flourishes and self-serving exaggerations and simplifications. But sooner or later, the realities assert themselves. People grasp that they’ve been misled. They feel betrayed; there’s a backlash.

The job of the president is not merely to inspire. It is first and foremost to inform — to help people see the world as it is, not as they wish it to be — and then to craft policies based on that understanding. Barack Obama is so confident of his rhetorical powers that he violates such self-restraint. In his speech, he casually mentioned “hard choices” but didn’t say what they are; he offhandedly acknowledged that combatting climate change will be “long” but didn’t say why. His make-believe assumptions sound good but will have a short shelf life.