The "concrete universal" is a key concept in Mou Zongsan's 牟宗三 (1909-1995) philosophy. Mou makes use of this concept in his metaphysics, ethics and philosophy of history. According to Mou, concrete universality is an attribute of the original heart as a spiritual substance. The original heart is universal since it is the faculty that initiates moral actions in response to individual situations. It is concrete in that it has a determinate content only in its response to a given situation. However, Mou also characterizes the original heart as a concrete universal because every individual person displays the original heart in his own way and in a different degree. Rooted in Mou's moral metaphysics, the idea that the original heart is a concrete universal implies a specific doctrine of moral action.