Classification theory..

Hello, I am looking for papers which interpret the conceptual framework (Stability, Simplicity..) of Shelah's Classification theory in purely categorical terminology. In spite of a remark (page 58, Accessible Categories: Makkai and Pare/ Cont maths 104) `one of the chief aims of clasification theory as pursued by S.Shelah is to answer a purely categorical inquiry about completely elemntary categories.' I have not been able to find further information about this aspect. I will be grateful for any pointers. Sincerely, P.S.Subramanian, Tata Institute.