According to Zhu Xi, knowledge and action were indivisible components of truly intelligent activity. Although he did distinguish (tell apart) between the priority of knowing, since intelligent action requires forethought (thought before), and the importance of action, as it produces a discernible effect, Zhu Xi said "Knowledge and action always require each other. It is like a person who cannot walk without legs although he has eyes, and who cannot see without eyes although he has legs. With respect to order, knowledge comes first, and with respect to importance, action is more important."