Prof. Han Jingqing's milestone paper of 1989: 'Control theory: the doctrine of model or the doctrine of control'showed his deep understanding and complete grasp of the science and engineering of control and it laid the foundation for active disturbance rejection control (ADRC). It is both the origin and the gateway through which ADRC is to be truly understood. To take his critical reflection further, this paper strives to clarify and reflect on the paradigm and foundation of the the doctrine of control, and to continue to explore the essence and significance of ADRC, for the purpose of facilitating further development of ADRC, in theory and in technology.