Erickson had a theory of change – not a theory of personality structure. The thing to keep in mind about this might be best compared to learning in other areas. Take a martial art, like Aikido, for instance. There is a theory that can be taught and learned but it is not a theory around the content of the attacker. The Nage (practitioner) does not care if the attacker is old or young, rich or poor, nervous or angry, mean or self critical, mugging or borrowing, bragging or complaining, robbing or hurting, conflicted or certain, character disordered or psychotic, traumatized at a preverbal age or chronically, depressed due to childhood neglect or the current situation, had the attacking mood for years or just a couple of minutes, etc. These things are probably of interest to conventional psychology and any therapy that uses a theory of personality. Aikido does care about what direction the person is going. Also of importance is how they have initiate the attack, where the center of the attack is located, where their balance and center is at the moment, the speed and rhythm of the movement, etc. These dynamic and technical matters are what the theory is based upon. It is a theory of change. So too, it would seem, is Erickson’s theory.