From Chapter 5 …

Though Stevie’s manner of functioning may be simpler than that of Steven, the structure of Stevie’s identity is actually more complex. Whereas the ego of Steven is centered in a unitary core, Stevie possesses an alter ego: the presence of “another” is found in his midst. Such a dimorphic feature is to be expected of the young child, since, at this early stage of development, identity has not yet crystallized into the singular form it will later assume (the structure of the child’s identity reflects the polymorphous complexity of mythic identity noted at the outset of the previous chapter). Young children often have “imaginary” playmates or companions, a “departure from reality” that adults tend to discourage, or tolerate condescendingly.