Why Superman does what he does

Mark Waid on truly rational self-interest:

How does Kal-El connect with the world around him? Not by turning his back on his alien heritage, though that was certainly his instinct while he was growing up in a small town. No, he ultimately connects by embracing that heritage — by creating as an adult a new identity for himself that is as Kryptonian as Clark Kent is human. Kal-El knows instinctively that it is only when he puts his gifts to use that he truly feels alive and engaged. Only by acting to his fullest potential, rather than hiding on the sidelines behind a pair of fake eyeglasses, can he genuinely participate in the world around him. Only by being openly Kryptonian can he also be an Earthman with exuberance and excellence. When he lives as who he really is, in full authenticity to his nature and gifts, and then brings his distinctive strengths into the service of others, he takes his rightful place in the larger community, in which he now genuinely belongs and can feel fulfilled. It is no coincidence that, when the philosopher Aristotle (384-322BC) wanted to understand the roots of happiness, he began to explore what it takes to live with excellence. Superman, in his own way, discovered the same connection.