ASPEN, Colo.—Tech investor Peter Thiel, who founded PayPal, told an Aspen Ideas Festival crowd Wednesday that while highly regarded institutions of higher education claim to benefit society as a whole, the ultimate worth of the degrees they confer is actually inextricably tied to deliberate, ruthlessly enforced exclusivity. “What is the nature of the educational good?” Thiel said during an interview with David Bradley, the owner and chairman of Atlantic Media.