The underlying principle of Good Inside, as the title suggests, is that everyone is fundamentally good inside. Dr. Kennedy brings up the idea in the Introduction; it is also first on her list of 10 parenting principles, is further emphasized in every parenting strategy she offers, and is underlined in the conclusion as well.

The principle of inner goodness is what defines and feeds into every other principle Dr. Kennedy presents. Remembering inner goodness empowers parents to view behavior as a window because behavior doesn’t equal identity—it merely points to the underlying struggles that emerge from normal emotions. Inner goodness also informs the principle that two things can be true at once, suggesting that it is possible to be a good person and still struggle with things. It is also important to recognize and reduce shame because doing so helps reinforce an individual’s inherent goodness. Even the principle of self-care caters to this idea, as parents need to replenish their inner resources to be better parents and models to their children.

This last principle highlights that inner goodness is not applicable to children alone. In fact, Dr. Kennedy’s writing is directed entirely at parents, and she asserts that parenting is a process through which adults, too, understand their own upbringings better and grow and develop alongside their children.