Restating Kierkegaard, the cultural historian Louis Menand noted, Anxiety is the price tag on human freedom.2 Kierkegaard believed that we are free to choose our future actions, and this defines who we are.3 But modern science has concluded that our freedom is often more illusory than we think.4 Regardless of how free our will really is, though, the fact that we believe it is free makes us anxious when we perceive that we do not actually have control, when we face risky options in situations of uncertainty, or when we ruminate over how the present and future might be different if we had acted differently in the past.