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 . Although he did distinguish between the priority of knowing , since intelligent action requires forethought , and the importance of action , as it produces a discernible effect , Zhu Xi said `` Knowledge and action always require each other .