The most obvious thing about yourself is your self. "You look down at your body and know it's yours," says Todd Heatherton, a psychologist at Dartmouth University. "You know it's your hand you're controlling when you reach out. When you have memories, you know that they are yours and not someone else's. When you wake up in the morning, you don't have to interrogate yourself for a long time about who you are."
The self may be obvious, but it is also an enigma. Heatherton himself shied away from direct study of it for years, even though he had been exploring self-control, self-esteem and other related issues since graduate school. "My interests were all around the self but not around the philosophical issue of what is the self," he explains. "I avoided speculations about what it means. Or I tried to, anyway."