About the Naive/Innocent Inner Child
Do you know anyone who is notably "childlike," gullible, and naive? They may be often controlled by a normal personality subself who is Lost developmentally very young, innocent, and over-trusting. This Inner Child knows little of the real world, and is unaware of environmental and social dangers, and/or s/he unrealistically assumes that nothing can harm him or her.
Like other Inner Kids, the Naive Child may live in the past. S/He may not know there are other subselves, including an attentive Nurturer and wise true Self. If this child takes the host person over, s/he is apt to be vulnerable to toxic people, and make unwise decisions and get hurt. That can trigger the Hurt, Anxious, Loner, and Angry Inner Kids and a variety of their dedicated Guardian subselves.
This cycle of innocence > vulnerability/mistakes > reactive behaviors may cause the host person to appear "moody" or "split." ("One day she's naive and trusting, and the next day she's cynical, guarded, and withdrawn.")
When supervised, educated, and protected by the Nurturer and other Manager subselves, the Naive Child can provide richness and optimism to the host person's personality.