His heritage and breeding, along with the hardwiring of his brain, made him at times callous and impulsive. It also led to an exceedingly high tolerance for risk. He could calculate it coldly and also embrace it feverishly. “Elon wants risk for its own sake,” says Peter Thiel, who became his partner in the early days of PayPal. “He seems to enjoy it, indeed at times be addicted to it.”