When a person has a sense of themself as a definite identity, what makes it up? How does it come into existence? Does it arise from innate tendencies, or from external influence? Nature or nurture?
(As for the question of whether identities really exist or not, or whether they ought to exist or not, I already started a different great debate on that.)
Self-awareness + discrimination = identity
There’s one theory that says it arises in the infant from stress. That babies start out “thinking” they are simply extensions of their mothers (or, more precisely, that their mothers are extensions of them, like an extra set of legs and arms) and all is well with the world. Gradually, the infant is stressed by mom’s absence or slowness in responding to the baby. The baby first realizes that he has no control over his mother’s arms and legs, and eventually realizes through the first year that they are separate entities. Identity is gradually formed as the infant separates the world into two categories: “me” and “not-me”. Playing with toes, smacking things, throwing things - all these are experiments our little scientist is doing to determine where exactly she ends and the rest of the world begins.
If you think about it that way, it’s no wonder babies begin to suffer separation anxiety around 8 or 9 months. It’d be pretty freaking awful to realize that your legs didn’t belong to you, wouldn’t it?