Mark Zuckerberg's 7-year-old daughter told him she wanted to be Taylor Swift when she grew up. He looked at her and said you can't, that's not available to you. Sounds brutal for a dad to say. But Zuckerberg built a $1.4 trillion company on the exact impulse he just shut down in his own kid, and he understands that impulse better than anyone alive. There's a French philosopher buried in this story. René Girard taught at Stanford, and his big idea was that desire is borrowed. You don't…