Study of the evolution of the doctrine of suffering

Dukkha as the most important teaching of Buddhism has passed a different process during Buddhism history and its schools, with respect to the reality of the suffering and the salvation. In early teachings of Buddha and in the form of four noble truths, it is emphasized and forms special philosophical and ideological system, especially in Travada tradition. But this doctrine in the tradition of Mahayana, such as other teachings (Karma, Samsara, Nirvana,) is influenced by Sunyata or nothing. Finally in Zen, as one of Mahayana schools in Far East, it improves with wu-hesin or no-mind teaching, and the fact of suffering in it decreases. Subsequently, it changes the practical ways and the path of deliverance from suffering in the branches of this school.