This paper proves the consistency of the system S4.1 acquired by adding the axiom M on the basis of the strict implication system S4.

• 文献[7]证明了严格蕴涵系统S4的协调性，本文证明在严格蕴涵系统S4的基础上增加公理M所得到的系统S4.；1的协调性。