Rationality gives us greater knowledge and greater control over our own actions and emotions and over the world. Although our rationality is, initially, an evolved quality—the nature of rationality includes the Nature in it—it enables us to transform ourselves and hence transcend our status as mere animals, actually and also symbolically. Rationality comes to shape and control its own function.
Our principles fix what our life stands for, our aims create the light our life is bathed in, and our rationality, both individual and coordinate, defines and symbolizes the distance we have come from mere animality. It is by these means that our lives can come to mean more than what they instrumentally yield. And by meaning more, our lives yield more.
-- Robert Nozick (The Nature of Rationality)