实践理性应用于三个层面的“应该”问题。实用层面的“应该”表现为在目标给定中对手段进行合理选择;价值层面的“应该”表现为对人生终极目的的抉择;道德层面的“应该”表现为在调节主体间利益冲突时所依据的道德原则。道德原则的实现以价值性“应该”问题的解决为前提。 Practical reasoning applies to the “should” issue at three levels. At the practical level, “should” be manifested in the reasonable choice of means in the given target; “should” in value should be expressed as the choice of the ultimate goal of life; in moral level, “should” be manifested in the adjustment of the conflicts of interests According to the moral principle. The realization of moral principles is premised on the solution of the problem of value “should”.